Controlled irrigation process and system for land application of wastewater

ABSTRACT

Systems, processes and methods for controlling the irrigation of wastewater to a vegetated land are provided. The process can include determining a drained upper limit (DUL)-related criterion of an irrigation zone of the vegetated land, and obtaining a soil water tension measurement indicative of the irrigation status in the irrigation zone. The soil water tension measurement can then be compared to the DUL-related criterion, and when the soil water tension measurement of the irrigation zone is equal to or above the DUL-related criterion, an irrigation event characterized by a given volume of wastewater and a given irrigation duration can be initiated to irrigate the irrigation zone. The process can also include implementing a predetermined irrigation protocol in accordance with a set of predetermined parameters to irrigate the irrigation zone during an irrigation event, the set of predetermined parameters including for instance a DUL-related criterion for the irrigation zone.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from U.S. provisional patentapplication No. 63/196,849, filed on Jun. 4, 2021, and entitled“CONTROLLED IRRIGATION PROCESS AND SYSTEM FOR LAND APPLICATION OFWASTEWATER”, the disclosure of which is hereby incorporated by referencein its entirety.

TECHNICAL FIELD

The technical field generally relates to techniques for treatingwastewater. In particular, the technical field relates to techniques forcontrolling wastewater irrigation in land application systems.

BACKGROUND

Land application systems involve the application of wastewater to avegetated land to treat wastewater and to provide a source of nutrientsand irrigation water to the vegetation and contribute to its growth.

Management of wastewater can give rise to several challenges. Forinstance, one of these challenges relates to the increase in volume ofwastewater that can occur when industries such as landfills andindustrial sites expand their activities, and/or due to the increase inprecipitation associated with climate change, and the lack of processingfacilities designed to cope with such increases in volume of wastewaterto be treated. Consequently, managing the excess wastewater ofteninvolves transporting the excess wastewater to another treatment site,which may not be desirable from an economic and environmental point ofview.

Another one of these challenges relates to the tightening of regulatoryrequirements requiring the industries managing wastewater to improve thequality of reclaimed water and/or, and to enhance recovery of resourcessuch as the water itself, and the nutrients that it contains, whilereducing levels of metals and other contaminants.

Land application systems are typically operated passively and thereforecan require a vegetated land having a large surface area, which may notbe available, may be unattractive economically, and/or may prevent theuse of a membrane to contain the irrigated wastewater. Such passivesystems can also lead to an inadequate use of the resources that wouldbe otherwise offered by the land application system, and an increasedenvironmental risk associated with the potential leaching ofcontaminants, etc.

Furthermore, conventional irrigation technologies used in agricultureapplications are typically aimed at maximizing plant yield by minimizingthe amount of water applied, which is a strategy that can have drawbackswhen seeking to increase the volume of wastewater applied to thevegetation of a land application system. Instrumentation devices used inagriculture applications can also be influenced by the salt content ofthe soil solution analyzed, which can render their use unsuitable formonitoring or controlling the irrigation of wastewater in a landapplication system due to the often high, or variable, salt content ofthe wastewater effluents.

Therefore, there remain a number of challenges with respect to themanagement of wastewater using land application system.

SUMMARY

In accordance with an aspect, there is provided a process forcontrolling irrigation of wastewater to a vegetated land, comprising:

-   -   determining a drained upper limit (DUL)-related criterion of an        irrigation zone of the vegetated land; and    -   obtaining a soil water tension measurement indicative of an        irrigation status in the irrigation zone;    -   wherein when the soil water tension measurement of the        irrigation zone is equal to or above the DUL-related criterion,        irrigating the irrigation zone with a given volume of wastewater        during an irrigation event having a start irrigation time and an        end irrigation time defining an irrigation duration, the given        volume of wastewater being determined so as to maximize an        amount of the wastewater applied to the vegetated land over        time.

In some implementations, the process further comprises determining adifferential between the soil water tension measurement and theDUL-related criterion.

In some implementations, the irrigation duration is adjustable inaccordance with the differential between the soil water tensionmeasurement and the DUL-related criterion.

In some implementations, the irrigation duration is adjustable tomaintain the soil water tension measurement above the DUL-relatedcriterion.

In some implementations, the given volume of wastewater is adjustable inaccordance with the differential between the soil water tensionmeasurement and the DUL-related criterion.

In some implementations, the given volume of wastewater is adjustable tomaintain the soil water tension measurement above the DUL-relatedcriterion.

In some implementations, the DUL-related criterion corresponds to a DULof the irrigation zone to which is added a percentage of a differencebetween the DUL and a wilting point of the irrigation zone, thepercentage being below 30%.

In some implementations, the DUL-related criterion corresponds to a DULof the irrigation zone.

In some implementations, determining the DUL-related criterioncomprises:

-   -   determining a DUL of the irrigation zone, comprising:    -   obtaining a series of soil water tension measurements on the        irrigation zone during a series of characterized events;    -   determining a soil tension loss of the irrigation zone following        a test irrigation event performed when the irrigation zone is        near the DUL; and    -   adding the soil tension loss to the DUL to obtain the        DUL-related criterion.

In some implementations, the DUL-related criterion correspond to “DUL+1irrigation event”.

In some implementations, the DUL-related criterion correspond to “DUL+xirrigation event”.

In some implementations, x is greater than 1.

In some implementations, x is an integer or a number with a fractionalcomponent.

In some implementations, when the soil water tension measurement of theirrigation zone is equal to or above the DUL-related criterion, thegiven volume of wastewater applied during the irrigation event isincreased by a factor corresponding to x.

In some implementations, when the soil water tension measurement of theirrigation zone is equal to or above the DUL-related criterion, and theirrigation duration is increased by a factor related to x.

In some implementations, the series of characterized events comprises atleast one of a planned irrigation event or a rainfall event.

In some implementations, the process further comprises characterizing asoil sample from the irrigation zone during a startup phase to obtain asoil characterization profile of the soil sample.

In some implementations, the given volume of wastewater corresponds to aportion of a maximum daily irrigation volume of wastewater applicable tothe irrigation zone.

In some implementations, the process further comprises determining awastewater characterization profile of the wastewater to obtaininformation relative to a contaminant load of the wastewater.

In some implementations, the maximum daily irrigation volume ofwastewater is determined at least in part according to the wastewatercharacterization profile.

In some implementations, the maximum daily irrigation volume ofwastewater is determined at least in part according to the soilcharacterization profile.

In some implementations, obtaining the soil water tension measurement isperformed using a tensiometer.

In some implementations, when the soil water tension measurement of theirrigation zone is below the DUL-related criterion, no wastewater isapplied to the irrigation zone.

In some implementations, the vegetated land comprises a short rotationwoody crop vegetation filter.

In some implementations, the irrigation zone comprises a plurality ofirrigation zones, and the process further comprises:

determining a corresponding DUL-related criterion for each irrigationzone of the plurality of irrigation zones; and

obtaining a corresponding soil water tension measurement for eachirrigation zone of the plurality of irrigation zones.

In some implementations, when more than one corresponding soil watertension measurement is above the corresponding DUL-related criterion,irrigating the irrigation zone having the largest differential betweenthe corresponding soil water tension measurement and the correspondingDUL-related criterion.

In accordance with another aspect, there is provided a method forcontrolling irrigation of wastewater onto an irrigation zone of avegetated land, comprising:

-   -   establishing a predetermined irrigation protocol in accordance        with a set of predetermined parameters to irrigate the        irrigation zone during an irrigation event having a start        irrigation time and an end irrigation time, the set of        predetermined parameters comprising:        -   an irrigation schedule corresponding to a time period during            which irrigation is determined to be suitable; and        -   an irrigation volume threshold indicative of a predetermined            cumulative volume of wastewater applicable to the irrigation            zone;        -   and at least one of:        -   a soaking time indicative of a delay between two successive            irrigation events in a same irrigation zone;        -   a rainfall intensity threshold at which or below which            irrigation is determined to be suitable;        -   a forecasted rainfall intensity; and        -   a DUL-related criterion for the irrigation zone.

In accordance with another aspect, there is provided a process forcontrolling irrigation of wastewater onto an irrigation zone of avegetated land, comprising:

-   -   implementing a predetermined irrigation protocol in accordance        with a set of predetermined parameters to irrigate the        irrigation zone during an irrigation event having a start        irrigation time and an end irrigation time defining an        irrigation duration, the set of predetermined parameters        comprising:        -   an irrigation schedule corresponding to a time period during            which irrigation is determined to be suitable;        -   a soaking time indicative of a delay between two successive            irrigation events in a same irrigation zone;        -   an irrigation volume threshold indicative of a predetermined            cumulative volume of wastewater applicable to the irrigation            zone;        -   a rainfall intensity threshold at which or below which            irrigation is determined to be suitable; and        -   a DUL-related criterion for the irrigation zone;    -   wherein when at least one of the start irrigation time is        outside of the irrigation schedule, a prior irrigation time is        less than the soaking time, a total daily irrigation volume is        equal or above the irrigation volume threshold, the rainfall        intensity is above the rainfall intensity threshold, and a soil        water tension measurement of the irrigation zone is below the        DUL-related criterion, no irrigation of wastewater is provided        to the irrigation zone; and    -   wherein when the start irrigation time is within the irrigation        schedule, the prior irrigation time is equal or more than the        soaking time, the total daily irrigation volume is below the        irrigation volume threshold, the rainfall intensity is below or        equal to the rainfall intensity threshold, and the soil water        tension measurement is equal to or above the DUL-related        criterion, irrigating the irrigation zone with wastewater.

In some implementations, the process further comprises determining awastewater characterization profile of the wastewater to obtaininformation relative to a contaminant load of the wastewater.

In some implementations, the irrigation volume threshold is determinedat least in part according to the wastewater characterization profile.

In some implementations, determining the wastewater characterizationprofile of the wastewater comprises determining at least one of totalsuspended solids (TSS), a chemical oxygen demand (COD), a biologicaloxygen demand (BOD5), a total nitrogen (TN), a total Kjeldahl nitrogen(TKN), total phosphorus (TP), NOx, NH4, alkalinity, a pH, and an ioniccompound concentration.

In some implementations, the irrigation schedule is determined accordingto a photoperiod representative of a time of year when the predeterminedirrigation protocol is intended to be implanted.

In some implementations, the predetermined irrigation protocolautomatically adjusts the photoperiod throughout the time of year.

In some implementations, the irrigation schedule is adjusted inaccordance with availability of the wastewater to treat.

In some implementations, the process further comprises determining theDUL of the irrigation zone.

In some implementations, determining the DUL comprises obtaining aseries of soil water tension measurements on the irrigation zone duringa startup phase.

In some implementations, obtaining the series of soil water tensionmeasurements on the irrigation zone during the startup phase isperformed during a series of characterized events.

In some implementations, the series of characterized events comprises atleast one of an irrigation event or a rainfall event that is significantenough to saturate the soil.

In some implementations, the process further comprises characterizing asoil sample from the irrigation zone during the startup phase to obtainthe soil characterization profile of the soil sample.

In some implementations, the DUL is determined according to the seriesof characterized events and the soil characterization profile of thesoil sample.

In some implementations, the soaking time is determined at least in partaccording to the soil characterization profile of the irrigation zone.

In some implementations, the irrigation volume threshold is determinedat least in part according to a soil characterization profile of theirrigation zone.

In some implementations, the soil characterization profile comprises agranulometric characteristic.

In some implementations, determining the DUL further comprisesvalidating the DUL at a given timepoint during the implementation of thepredetermined irrigation protocol or following an additional rainfallevent.

In some implementations, the soaking time is between 2 minutes and 60minutes.

In some implementations, the irrigation duration is between 5 minutesand 60 minutes.

In some implementations, the irrigation duration period is determinedsuch that the soil water tension remains above the DUL.

In some implementations, the predetermined irrigation protocol isrepeated in alternance with the soaking time over a period of 24 hours.

In some implementations, the predetermined irrigation protocol isrepeated between 0 times and 30 times over the period of 24 hours.

In accordance with another aspect, there is provided a process forcontrolling irrigation of wastewater onto an irrigation zone of avegetated land, comprising:

-   -   implementing a predetermined irrigation protocol in accordance        with a set of predetermined parameters to irrigate the        irrigation zone during an irrigation event having a start        irrigation time and an end irrigation time defining an        irrigation duration, the set of predetermined parameters        comprising:        -   an irrigation schedule corresponding to a time period during            which irrigation is determined to be suitable;        -   a soaking time indicative of a delay between two successive            irrigation events in a same irrigation zone;        -   an irrigation volume threshold indicative of a predetermined            cumulative volume of wastewater applicable onto the            irrigation zone; and        -   a DUL-related criterion for the irrigation zone;    -   wherein when at least one of the start irrigation time is        outside of the irrigation schedule, a prior irrigation time is        less than the soaking time, a total daily irrigation volume is        equal or above the irrigation volume threshold, or a soil water        tension measurement of the irrigation zone is below the        DUL-related criterion, no irrigation of wastewater is provided        to the irrigation zone; and    -   wherein when the start irrigation time is within the irrigation        schedule, the prior irrigation time is equal or more than the        soaking time, the total daily irrigation volume is below the        irrigation volume threshold, and the soil water tension        measurement is equal to or above the DUL-related criterion,        irrigating the irrigation zone with wastewater.

In some implementations, the set of predetermined parameters furthercomprises a rainfall intensity threshold at which or below whichirrigation is determined to be suitable; and

-   -   wherein when at least one of the start irrigation time is        outside of the irrigation schedule, a prior irrigation time is        less than the soaking time, a total daily irrigation volume is        equal or above the irrigation volume threshold, a soil water        tension measurement of the irrigation zone is below the        DUL-related criterion, or the rainfall intensity is above the        rainfall intensity threshold, no irrigation of wastewater is        provided to the irrigation zone; and    -   wherein when the start irrigation time is within the irrigation        schedule, the prior irrigation time is equal or more than the        soaking time, the total daily irrigation volume is below the        irrigation volume threshold, the soil water tension measurement        is equal to or above the DUL-related criterion, and the rainfall        intensity is below or equal to the rainfall intensity threshold,        irrigating the irrigation zone with wastewater.

In some implementations, the set of predetermined parameters furthercomprises a forecasted rainfall intensity threshold at which or belowwhich irrigation is determined to be suitable; and

-   -   wherein when at least one of the start irrigation time is        outside of the irrigation schedule, a prior irrigation time is        less than the soaking time, a total daily irrigation volume is        equal or above the irrigation volume threshold, a soil water        tension measurement of the irrigation zone is below the        DUL-related criterion, the rainfall intensity is above the        rainfall intensity threshold, or the forecasted rainfall        intensity is above a forecasted rainfall intensity threshold in        less than a given number of minutes, no irrigation of wastewater        is provided to the irrigation zone; and    -   wherein when the start irrigation time is within the irrigation        schedule, the prior irrigation time is equal or more than the        soaking time, the total daily irrigation volume is below the        irrigation volume threshold, the soil water tension measurement        is equal to or above the DUL-related criterion, the rainfall        intensity is below or equal to the rainfall intensity threshold,        and the forecasted rainfall intensity is equal or below the        forecasted rainfall intensity threshold for a given number of        minutes or the forecasted rainfall intensity is higher than the        forecasted rainfall intensity threshold but after the given        number of minutes, irrigating the irrigation zone with        wastewater.

In some implementations, the process further comprises determining awastewater characterization profile of the wastewater to obtaininformation relative to a contaminant load of the wastewater.

In some implementations, the irrigation volume threshold is determinedat least in part according to the wastewater characterization profile.

In some implementations, determining the wastewater characterizationprofile of the wastewater comprises determining at least one of totalsuspended solids (TSS), a chemical oxygen demand (COD), a biologicaloxygen demand (BOD5), a total nitrogen (TN), a total Kjeldahl nitrogen(TKN), total phosphorus (TP), NOx, NH4, alkalinity, a pH, and an ioniccompound concentration.

In some implementations, the irrigation schedule is determined accordingto a photoperiod representative of a time of year when the predeterminedirrigation protocol is intended to be implanted.

In some implementations, the predetermined irrigation protocolautomatically adjusts the photoperiod throughout the time of year.

In some implementations, the irrigation schedule is adjusted inaccordance with availability of the wastewater to treat.

In some implementations, the process further comprises determining a DULof the irrigation zone.

In some implementations, determining the DUL comprises obtaining aseries of soil water tension measurements on the irrigation zone duringa startup phase.

In some implementations, obtaining the series of soil water tensionmeasurements on the irrigation zone during the startup phase isperformed during a series of characterized events.

In some implementations, the series of characterized events comprises atleast one of an irrigation event or a rainfall event that is significantenough to saturate the soil.

In some implementations, the process further comprises characterizing asoil sample from the irrigation zone during the startup phase to obtainthe soil characterization profile of the soil sample.

In some implementations, the DUL is determined according to the seriesof characterized events and the soil characterization profile of thesoil sample.

In some implementations, the soaking time is determined at least in partaccording to the soil characterization profile.

In some implementations, the irrigation volume threshold is determinedat least in part according to a soil characterization profile of theirrigation zone.

In some implementations, the soil characterization profile comprises agranulometric characteristic.

In some implementations, determining the DUL further comprisesvalidating the DUL at a given timepoint during the implementation of thepredetermined irrigation protocol or following an additional rainfallevent.

In some implementations, the soaking time is between 2 minutes and 60minutes.

In some implementations, the irrigation duration is between 5 minutesand 60 minutes.

In some implementations, the irrigation duration period is determinedsuch that the soil water tension remains above the DUL.

In some implementations, the predetermined irrigation protocol isrepeated in alternance with the soaking time over a period of 24 hours.

In some implementations, the predetermined irrigation protocol isrepeated between 0 times and 30 times over the period of 24 hours.

In accordance with another aspect, there is provided a process forcontrolling irrigation of wastewater onto an irrigation zone of avegetated land, comprising:

-   -   implementing a predetermined irrigation protocol in accordance        with a set of predetermined parameters to irrigate the        irrigation zone during an irrigation event having a start        irrigation time and an end irrigation time defining an        irrigation duration, the set of predetermined parameters        comprising:        -   an irrigation schedule corresponding to a time period during            which irrigation is determined to be suitable;        -   a soaking time indicative of a delay between two successive            irrigation events in a same irrigation zone;        -   an irrigation volume threshold indicative of a predetermined            cumulative volume of wastewater applicable onto the            irrigation zone; and        -   a rainfall intensity threshold at which or below which            irrigation is determined to be suitable;    -   wherein when at least one of the start irrigation time is        outside of the irrigation schedule, a prior irrigation time is        less than the soaking time, a total daily irrigation volume is        equal or above the irrigation volume threshold, and the rainfall        intensity is above the rainfall intensity threshold, no        irrigation of wastewater is provided to the irrigation zone; and    -   wherein when the start irrigation time is within the irrigation        schedule, the prior irrigation time is equal or more than the        soaking time, the total daily irrigation volume is below the        irrigation volume threshold, and the rainfall intensity is below        or equal to the rainfall intensity threshold, irrigating the        irrigation zone with wastewater.

In accordance with another aspect, there is provided a process forcontrolling irrigation of wastewater onto an irrigation zone of avegetated land, comprising:

-   -   implementing a predetermined irrigation protocol in accordance        with a set of predetermined parameters to irrigate the        irrigation zone during an irrigation event having a start        irrigation time and an end irrigation time defining an        irrigation duration, the set of predetermined parameters        comprising:        -   an irrigation schedule corresponding to a time period during            which irrigation is determined to be suitable;        -   a soaking time indicative of a delay between two successive            irrigation events in a same irrigation zone; and        -   an irrigation volume threshold indicative of a predetermined            cumulative volume of wastewater applicable onto the            irrigation zone; and    -   wherein when at least one of the start irrigation time is        outside of the irrigation schedule, a prior irrigation time is        less than the soaking time, and a total daily irrigation volume        is equal or above the irrigation volume threshold, no irrigation        of wastewater is provided to the irrigation zone; and    -   wherein when the start irrigation time is within the irrigation        schedule, the prior irrigation time is equal or more than the        soaking time, and the total daily irrigation volume is below the        irrigation volume threshold, irrigating the irrigation zone with        wastewater.

In accordance with another aspect, there is provided a system forcontrolling irrigation of wastewater onto a vegetated land comprising anirrigation zone, comprising:

-   -   a pumping station comprising a pump in fluid communication with        a wastewater source for supplying the wastewater to the        irrigation zone;    -   an irrigation network in fluid communication with the pump for        supplying a volume of the wastewater to the irrigation zone;    -   a control station comprising a controller operatively connected        to the pump; and    -   a soil water tension measuring device for measuring a soil water        tension of the irrigation zone, the soil water tension measuring        device being operatively connected to the controller to transmit        data from the soil water tension measuring device to the        controller, the controller being further configured to evaluate        the soil water tension with respect to a drained upper limit and        to initiate an irrigation event when the soil water tension        measurement of the irrigation zone is equal to or above the        drained upper limit.

In some implementations, the controller is configured to provideinstruction to the pump regarding an irrigation duration of theirrigation event.

In some implementations, the irrigation network comprises a surfaceirrigation system for supplying the wastewater to the irrigation zone.

In some implementations, the surface irrigation system comprises asurface drip system.

In some implementations, the surface irrigation system comprises amicro-sprinkler system.

In some implementations, the micro-sprinkler system comprises a pivotirrigation system or a boom irrigation system.

In some implementations, the irrigation network further comprises apipeline fluidly connecting the pump with the surface irrigation system.

In some implementations, the irrigation network comprises an undergroundirrigation system for supplying the wastewater to the irrigation zone.

In some implementations, the underground irrigation system comprises aburied drip system.

In some implementations, the irrigation network further comprises apipeline fluidly connecting the pump with the underground irrigationsystem.

In some implementations, the irrigation network further comprises anin-line pressure sensor configured to measure an upstream pressure ofthe irrigation network.

In some implementations, the in-line pressure sensor is furtherconfigured to monitor hydraulic properties of the irrigation network.

In some implementations, the in-line pressure sensor is operativelyconnected to the pump to stop operation of the pump when the upstreampressure is above or below a given pressure threshold.

In some implementations, the irrigation network further comprises aflowmeter configured to measure a flow of wastewater flowing in theirrigation network.

In some implementations, the flowmeter is further configured to measurethe volume of irrigated wastewater supplied to the irrigation zone.

In some implementations, the irrigation network further comprises anirrigation valve provided upstream of the irrigation zone, theirrigation valve being configured to modulate the volume of wastewatersupplied to the irrigation zone.

In some implementations, the system further comprises a weather stationcomprising a weather monitoring instrument.

In some implementations, the weather monitoring instrument comprises oneor more of a temperature sensor, a humidity sensor, a rain gauge, asolar radiation probe and an anemometer.

In some implementations, the weather monitoring instrument is a raingauge to measure a rainfall intensity.

In some implementations, the rain gauge is operatively connected to thecontroller, and the controller is further configured to adjust thevolume of wastewater supplied to the irrigation zone in accordance withthe rainfall intensity.

In some implementations, the controller is configured to process atleast one signal generated by the weather station.

In some implementations, the controller is configured to process atleast one signal generated by the pumping station.

In some implementations, the controller is configured to process atleast one signal generated by the soil water tension measuring device.

In some implementations, the system further comprises a memoryconfigured to store information representative of at least one of a pastirrigation status of the irrigation zone, an ongoing irrigation statusof the irrigation or a forecasted irrigation status of the irrigationzone.

In some implementations, the memory is integrated to the controller.

In some implementations, the memory is in data communication with thecontroller.

In some implementations, the memory is further configured to storecalibration data.

In some implementations, the calibration data is representative ofcontrol parameters of at least one of the pumping station and the soiltension measuring device.

In some implementations, the system further comprises a user interfaceconfigured to control the system through the control station.

In some implementations, the user interface is a graphical userinterface.

In some implementations, the user interface is part of a web-basedapplication.

In some implementations, the user interface is part of a cloud-basedplatform.

In some implementations, the system further comprises a predictionmodule in data communication with the control station, the predictionmodule being configured to output an estimate of the soil water tensionbased on information representative of at least one of weatherconditions, actual soil tension or hydraulic loading to be applied.

In some implementations, the estimate of the soil water tension isrepresentative of an instantaneous soil water tension.

In accordance with another aspect, there is provided a controller for asystem for controlling irrigation of wastewater onto a vegetated land,the vegetated land comprising an irrigation zone, the controller beingin data communication with a pumping station comprising a pump, thecontroller being configured to:

-   -   determine a soil water tension of the irrigation zone with        respect to a drained upper limit; and    -   send instructions to the pump of the pumping station to initiate        an irrigation event when the soil water tension measurement of        the irrigation zone is equal to or above the drained upper        limit.

In some implementations, the controller is further configured to obtaindata from the pumping station.

In some implementations, the controller is further configured to processat least one signal generated by the pumping station.

In some implementations, the system further includes a weather station,the controller being further configured to obtain data from the weatherstation.

In some implementations, the controller is further configured to processat least one signal generated by the weather station.

In some implementations, the system further includes a soil watertension measuring device, the controller being further configured toobtain data from the soil water tension measuring device.

In some implementations, the controller is further configured to processat least one signal generated by the soil water tension measuringdevice.

In accordance with another aspect, there is provided a process forcontrolling irrigation of wastewater to a vegetated land, comprising:

-   -   obtaining a soil water tension measurement indicative of the        irrigation status in the irrigation zone;    -   wherein when the soil water tension measurement of the        irrigation zone is equal to or above a DUL-related criterion,        irrigating the irrigation zone with a given volume of wastewater        during an irrigation event having a start irrigation time and an        end irrigation time defining an irrigation duration, the given        volume of wastewater being determined so as to maximize an        amount of the wastewater applied to the vegetated land over        time.

In some implementations, the process further comprises determining adifferential between the soil water tension measurement and theDUL-related criterion.

In some implementations, the irrigation duration is adjustable inaccordance with the differential between the soil water tensionmeasurement and the DUL-related criterion.

In some implementations, the irrigation duration is adjustable tomaintain the soil water tension measurement above the DUL-relatedcriterion.

In some implementations, the given volume of wastewater is adjustable inaccordance with the differential between the soil water tensionmeasurement and the DUL-related criterion.

In some implementations, the given volume of wastewater is adjustable tomaintain the soil water tension measurement above the DUL-relatedcriterion.

In some implementations, the DUL-related criterion corresponds to a DULof the irrigation zone to which is added a percentage of a differencebetween the DUL and a wilting point of the irrigation zone, thepercentage being below 30%.

In some implementations, the DUL-related criterion corresponds to a DULof the irrigation zone.

In some implementations, determining the DUL-related criterioncomprises:

-   -   determining a DUL of the irrigation zone, comprising:    -   obtaining a series of soil water tension measurements on the        irrigation zone during a series of characterized events;    -   determining a soil tension loss of the irrigation zone following        a test irrigation event performed when the irrigation zone is        near the DUL; and    -   adding the soil tension loss to the DUL to obtain the        DUL-related criterion.

In some implementations, the DUL-related criterion correspond to “DUL+1irrigation event”.

In some implementations, the DUL-related criterion correspond to “DUL+xirrigation event”.

In some implementations, x is greater than 1.

In some implementations, x is an integer or a number with a fractionalcomponent.

In some implementations, when the soil water tension measurement of theirrigation zone is equal to or above the DUL-related criterion, thegiven volume of wastewater applied during the irrigation event isincreased by a factor corresponding to x.

In some implementations, when the soil water tension measurement of theirrigation zone is equal to or above the DUL-related criterion, and theirrigation duration is increased by a factor related to x.

In some implementations, the series of characterized events comprises atleast one of a planned irrigation event or a rainfall event.

In some implementations, the process further comprises characterizing asoil sample from the irrigation zone during a startup phase to obtain asoil characterization profile of the soil sample.

In some implementations, the given volume of wastewater corresponds to aportion of a maximum daily irrigation volume of wastewater applicable tothe irrigation zone.

In some implementations, the process further comprises determining awastewater characterization profile of the wastewater to obtaininformation relative to a contaminant load of the wastewater.

In some implementations, the maximum daily irrigation volume ofwastewater is determined at least in part according to the wastewatercharacterization profile.

In some implementations, the maximum daily irrigation volume ofwastewater is determined at least in part according to the soilcharacterization profile.

In some implementations, obtaining the soil water tension measurement isperformed using a tensiometer.

In some implementations, when the soil water tension measurement of theirrigation zone is below the DUL-related criterion, no wastewater isapplied to the irrigation zone.

In some implementations, the vegetated land comprises a short rotationwoody crop vegetation filter.

In some implementations, the irrigation zone comprises a plurality ofirrigation zones, and the process further comprises:

-   -   determining a corresponding DUL-related criterion for each        irrigation zone of the plurality of irrigation zones; and    -   obtaining a corresponding soil water tension measurement for        each irrigation zone of the plurality of irrigation zones.

In some implementations, when more than one corresponding soil watertension measurement is above the corresponding DUL-related criterion,irrigating the irrigation zone having the largest differential betweenthe corresponding soil water tension measurement and the correspondingDUL-related criterion.

In some implementations, the process, method, system and/or controllerfurther comprises one or more features as defined herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The figures of the present application illustrate various features,aspects and implementations of the technology described herein.

FIG. 1 is a schematic representation of a system for controlling theirrigation of a wastewater effluent to a vegetated land, in accordancewith an implementation, the system including a pumping station, acontrol station, and a weather station.

FIG. 2 is a schematic representation of an irrigation protocol thatincludes seven parameters, namely an irrigation schedule, a forecastedrainfall intensity, a soaking time, an irrigation volume threshold, arainfall intensity, a soil moisture, and an irrigation event duration.

FIG. 3 is a schematic representation of an irrigation protocol thatincludes six selected parameters.

FIG. 4 is a schematic representation of an irrigation protocol thatincludes five selected parameters.

FIG. 5 is a schematic representation of an irrigation protocol thatincludes five selected parameters.

FIG. 6 is a schematic representation of an irrigation protocol thatincludes four selected parameters.

DETAILED DESCRIPTION

Techniques described herein relate to processes and systems forcontrolling the irrigation of a wastewater effluent that containscontaminants to a vegetated land, or vegetated soil surface, as a meansto treat the wastewater effluent while producing a source of valuablebiomass. Controlling the application of a wastewater effluent via apredetermined irrigation protocol in the context of a land applicationsystem can achieve various objectives, such as enhancingevapotranspiration of the vegetation forming the vegetated land,reducing runoff and percolation of the irrigated wastewater into thesoil, and perpetuating the effectiveness of the treatment process bycontrolling the contaminant loading applied to the vegetated land.

In accordance with the techniques described herein, controlling theapplication of a wastewater effluent to an irrigation zone of avegetated land as part of a land application system can includeestablishing a predetermined irrigation protocol in accordance with aset of various predetermined parameters to control the irrigation of anirrigation zone during an irrigation event. The set of predeterminedparameters can include for instance one or more of an irrigationschedule corresponding to a time period during which irrigation isdetermined to be indicated, a soaking time indicative of a delay betweentwo successive irrigation events in a same irrigation zone, anirrigation volume threshold (or a maximum daily irrigation volume)applicable onto the irrigation zone, a rainfall intensity threshold atwhich or below which irrigation is determined to be indicated, and adrained upper limit of the irrigation zone. These predeterminedparameters can be evaluated at least against data representative of theirrigation status of the irrigation zone to determine whether anirrigation event is to be initiated or not.

When the set of predetermined parameters listed above are included in apredetermined irrigation protocol, implementing the predeterminedirrigation protocol can include evaluating if at least one of the startirrigation time is outside of the irrigation schedule, a priorirrigation time is less than the soaking time, a total daily irrigationvolume is equal or above the irrigation volume threshold, the rainfallintensity is above the rainfall intensity threshold, and a soil watertension measurement of the irrigation zone is below the drained upperlimit, in which case it can be determined that an irrigation event isnot to be initiated and that no irrigation of wastewater is to beprovided to the irrigation zone.

Alternatively, when the start irrigation time is within the irrigationschedule, the prior irrigation time is equal or more than the soakingtime, the total daily irrigation volume is below the irrigation volumethreshold, the rainfall intensity is below or equal to the rainfallintensity threshold, and the soil water tension measurement is equal toor above the drained upper limit, it can be determined that anirrigation event is to be initiated to irrigate the irrigation zone withwastewater.

Although various parameters are mentioned above, the irrigation protocolcan also include a selection of these parameters or additionalparameters, as the irrigation protocol can be adapted for a givenapplication land.

In accordance with the techniques described herein, a key parameterinfluencing the decision to initiate an irrigation event or not and thusfor controlling the irrigation of wastewater to a vegetated land is thesoil water tension of the irrigation zone. The soil water tension can bemonitored at a given location in the irrigation zone to obtain a soilwater tension measurement that is subsequently compared to a drainedupper limit of the irrigation zone. In some implementations, when thesoil water tension measurement of the irrigation zone is equal or abovethe drained upper limit, an irrigation event can be initiated toirrigate the irrigation zone with a given volume of wastewater. Thegiven volume of wastewater can be determined to maximize the volume ofwastewater applied to the vegetated land over a period of time whilereducing drainage out of the root zone of the vegetation, and can dependon factors such as the ability of the vegetation of the vegetated landto treat the wastewater via phytoremediation mechanisms, theevapotranspiration efficacy of the vegetation, and the soilcharacteristics.

Various implementations and features of the controlled wastewaterirrigation process and system will now be described in greater detail inthe following paragraphs.

General Overview of a Land Application System

A land application system involves the application of a wastewatereffluent to a vegetated land using various irrigation techniques such assurface irrigation or subsurface irrigation. Land application of awastewater effluent can provide several benefits, including providing asource of irrigation water and nutrients, such as nitrogen andphosphorus, to the vegetation of the vegetated land, offering aneconomical alternative to wastewater treatment by leveraging both theavailability of such wastewater as a source of irrigation and theavailability of vegetated land to receive the wastewater, providing analternative to costly infrastructures required to treat wastewater, andan opportunity to treat wastewater having certain contaminants thatwould be otherwise difficult to treat in conventional facilities.

In the context of the present description, the term “wastewater” canrefer to any source of water that includes various levels ofcontaminants and that is known in the art as being considered suitablefor land application systems. Examples of wastewater can includewastewater derived from farming activities, municipal wastewater,domestic wastewater, wastewater derived from industrial activities,sewage sludge, etc. The wastewater can be analyzed prior to beingapplied to the vegetated land to ensure that the concentration ofcontaminants, or other characteristics of the wastewater, falls withincertain ranges to determine whether the wastewater is suitable to besupplied to the vegetated land as an irrigation source. The wastewatercan be pre-treated prior to being applied to the vegetated land, forinstance to reduce the concentrations of certain contaminants.

Similarly, the vegetated land and soil suitability to receive thewastewater can depend on properties that can have the potential toimpact human or environmental health, for instance because of surfaceerosion or downward movement of contaminants through the soil. The siteproperties and soil characteristics can thus be assessed prior toinitiating operations involving the application of wastewater todetermine if the site is suitable as a land application system. Suchcharacterization can include for instance determining the primarydirection of surface drainage and the presence of slopes as propertiesof the site itself, and determining soil properties such as the pH,particle size distribution, permeability, porosity, density, claycontent, etc.

A land application system takes advantage of the ability of thevegetation and soil to perform vegetative uptake via evapotranspirationand thus reduce the volume of wastewater. Evapotranspiration combinesevaporation and transpiration mechanisms. Evaporation occurs when liquidwater is converted to water vapour and removed from an evaporationsurface, which can include the soil surface and the surface of theplant, including the leaves. The evaporation is dependent on factorssuch as solar radiation, which can be influenced by the extent of thevegetation canopy. Transpiration involves the vaporization of liquidwater contained in plant tissues and the vapour removal to theatmosphere following water take up by the roots and transport throughthe plant. The vaporization occurs within the leaf, in the intercellularspaces, and the transpiration then occurs through small openings in theplant leaf called stomata. Evapotranspiration thus represents the sum ofthese two types of water removal by the vegetation to the atmosphere.

Furthermore, the application of the wastewater effluent to the vegetatedland surface enables treatment of the wastewater effluent as it flowsthrough the plant root system and the soil matrix through variousphytoremediation mechanisms. For instance, the plant can absorbcontaminants such as nitrogen, potassium and phosphorus as inorganicnutrients. In particular, ammoniacal nitrogen can be absorbed by plantsroots or more likely, be nitrified to nitrate nitrogen by soilmicroorganisms and then be absorbed by plant roots. The root of theplant can also absorb other contaminants such as metals, e.g., Cd, Cr,Cu, Hg, Ni, Pb, and Zn to prevent their release to the environmentthrough percolation and runoff. In addition, vegetation, microorganismsand soil can contribute to reducing chemical oxygen demand (COD)concentrations, and biological oxygen demand (BOD₅) concentrations, andammonia concentrations in the water present in soil pores. Organicmatter can be removed by biological oxidation, filtration and adsorptionmechanisms.

Various factors can influence the performance of a land applicationsystem. Examples of these factors include the nature of the wastewater,the characteristics of the soil, particularly its structure andpermeability, prevailing winds, which assist evapotranspirationprocesses, the presence of shade which also influence evapotranspirationprocesses, existing vegetation, etc. A land application system can thusbe designed to find a balance between treatment of the wastewater andgrowth needs of the vegetation through evapotranspiration andpercolation.

The vegetation of the land application system can be chosen so as toproduce biomass that may or may not have an economic value. In someinstances, the vegetation can simply be ornamental, while in others, thebiomass produced can be harvested and used for various applications. Anexample of a suitable vegetation for use in a land application system isa short rotation willow coppice (SRWC) vegetation filter. Willow bedshave high rates of evapotranspiration, provide a biomass having aneconomic value, are non-edible, and have a high nitrogen and some metalabsorption capacity. In addition, willow beds have nitrogen, phosphorusand potassium proportional requirements similar to the proportion ofthese nutrients typically found in municipal wastewater, making SRWCvegetation filters appealing for the treatment of this type ofwastewater effluent. It is to be noted that a short rotation woodcoppice can also be referred to as a SRWC.

Although a SRWC vegetation filter has been described above as an exampleof vegetation for a land application system, it is to be understood thatany type of vegetation known in the art for use in the context of landapplication systems can be suitable for implementing the techniquesdescribed herein. Any fast-growing tree species, and particularly thosehaving a high evapotranspiration rate and enhanced tolerance of theirroot system to anaerobic conditions, can be a type of vegetation ofchoice for implementing a land application system suitable operatedaccording to the techniques described herein, since thesecharacteristics can facilitate the application of large amounts ofwastewater to the vegetated land. Rapid root, stem and leaf growth canalso provide rapid uptake of nutrients such as nitrogen and phosphorousand of water. Populus, bamboos, and eucalypts are additional examples ofshort-rotation woody species that can be suitable for land applicationsystems, among others. Any high evapotranspiration plants can also besuitable.

In some implementations, short rotation coppice of fast-growing treespecies can be particularly suitable, as this type of culture canprovide several benefits given the rapid root, stem and leaf growth ofthe vegetation. An example of a benefit provided by short rotationcoppice of fast-growing tree species is that the crop can be harvestedaccording to shorter harvest cycles and subsequently be quicklyreplaced, given the ability of some short rotation coppice to resproutfrom stumps after being harvested. Another example of benefit of shortrotation coppice of fast-growing tree species is that it can producebiomass that is valuable economically at a rapid rate.

As mentioned above, conventional techniques for applying wastewater to avegetated land are typically passive, and generally involve irrigatingthe vegetated at a constant daily hydraulic loading rate. These passiveland application systems may not be suitable for enhancingevapotranspiration when wastewater applied to the vegetated land isbelow the evapotranspiration capacity of the vegetation, whichtranslates in a suboptimal use of the vegetation resources. On the otherhand, supplying a constant volume of wastewater to the vegetated landcan result in saturated soil conditions, and thus in water runoff anddeep percolation. In addition, passive management of a land applicationsystem does not take into consideration constraints related to thetreatment efficiency of the process, such as the capacity of the soil todegrade organic matter or to nitrify the ammoniacal nitrogen brought bythe wastewater effluent.

Actively controlling the irrigation of wastewater in the context of aland application system can contribute to overcome some of thesedrawbacks.

Controlled Application of Wastewater to an Irrigation Zone of aVegetated Land

Processes and systems for controlling the application of a wastewatereffluent to an irrigation zone of a vegetated land will now be describedin further detail.

With reference to FIG. 1 , a schematic representation of a controlledirrigation system 10 that can be implemented to control the irrigationof a wastewater effluent from a wastewater source 12 to an irrigationzone 14 of a vegetated land 18 via an irrigation network 20 is shown. Inthe illustrated implementation, a first irrigation zone 14 and a secondirrigation zone 16 are shown.

It is to be noted that the vegetated land 18 can also be referred to asa “vegetation filter”, and that these two expressions are usedinterchangeably in the present description. In accordance with theconcepts described above, a vegetation filter can be defined as is aplant-based treatment system that involves phytoremediation strategiesfor treating wastewater through fast-growing woody trees and/orherbaceous perennials, relying on soil attenuation capacity, biologicaldegradation, and plant uptake to remove contaminants from thewastewater.

Considerations when selecting the type of vegetation for the vegetatedland can include root depths, irrigation requirements, growth cycle, andcompetition with other vegetation, to name a few. The choice ofvegetation can also be performed according to the nutrient needs of thevegetation of interest, to ensure that the wastewater that willeventually be supplied to the vegetation promote growth of thevegetation without addition of extraneous fertilizers while maintaininga satisfactory yield with respect to biomass production.

An irrigation zone 14, 16 can be defined as an area of the vegetatedland 18 that includes at least one monitoring device 42 for monitoring aproperty indicative of an irrigation status of the irrigation zone, andthat is supplied with a controlled amount, which can be expressed as avolume, of wastewater. In some implementations, the irrigation zone canbe supplied with a controlled amount of wastewater independently of anadjacent irrigation zone. The interaction between the data collected bythe monitoring device 42 regarding the irrigation status of theirrigation zone and the resulting controlled application of wastewateras an irrigation source for the irrigation zone can facilitate applyingan amount of wastewater for that given irrigation zone that is suitablefor its evapotranspiration capacity and/or treatment capacity, amongother factors.

The determination of an area of the vegetated land that can be suitablefor forming an irrigation zone can depend on the homogeneity of soilcharacteristics over the vegetated land. Examples of soilcharacteristics can include for instance particle size distribution,permeability, porosity, density, and clay content, or any other soilcharacteristic that can contribute to influence soil oxygenation and theretention of the irrigated wastewater by the soil. When the soil of thevegetated land is considered heterogenous, the number of irrigationzones can be increased, with each irrigation zone being provided with atleast one monitoring device. By increasing the number of irrigationzones, each monitoring device can collect data indicative of theirrigation status for a given section of the vegetated land that isconsidered somewhat homogenous, and be supplied with a controlled amountof wastewater in accordance with the data collected by the monitoringdevice. In other words, the vegetated land can be divided in a givennumber of irrigation zones that are determined as being substantiallyhomogenous in terms of their sol characteristics, with at least onemonitoring device being provided per irrigation zone. Providing morethan one monitoring device per irrigation zone can contribute toobtaining data as representative as possible of the entire irrigationzone, which in turn can facilitate the control of the irrigation of thatspecific irrigation zone. This aspect will be described in furtherdetail below.

In other implementations, the soil characteristics can be substantiallyhomogenous over the entire vegetated land, and the segmentation of thevegetated land into irrigation zones can depend on the optimization ofthe wastewater distribution over the vegetated land. For instance, thewastewater supply network, or irrigation network, can be designed tosupply wastewater to a certain area of the vegetated land, and suchsurface area would correspond to an irrigation zone.

Thus, an irrigation zone as described herein can be described as anysection of a vegetated land for which controlled irrigation can beachieved via the use of a monitoring device collecting data that isindicative of the irrigation status of the irrigation zone, andsubsequent application of a controlled amount of wastewater determinedat least in part in accordance with the collected data.

The wastewater source 12 can be any type of containment structureconfigured for holding a certain volume of wastewater that can then besupplied to an irrigation zone via the irrigation network 20. In someimplementations, the containment structure can be a holding tank. As theavailability of the wastewater as a source of irrigation water may varyover time depending on the industries or operations supplying it, thecontainment structure can be configured to be oversized to hold anadditional volume of wastewater that would enable satisfactory supply tothe irrigation zones over a given period of time to ensure that waterneeds of the vegetation are met. In some implementations, the wastewatersource 12 includes a float switch operating in an on/off manner toindicate to the pump 24 that enough wastewater is available to initiatean irrigation event, or alternatively that not enough wastewater isavailable to initiate an irrigation event.

As mentioned above, any source of water that includes contaminants andthat is considered suitable for land application systems can be used aswastewater for the controlled irrigation system 10 described herein.Examples of wastewater can include wastewater derived from farmingactivities, municipal wastewater, domestic wastewater, sewage sludge,landfill leachate, etc. A step of wastewater characterization can beperformed to evaluate the suitability of the wastewater to be applied asirrigation water, and/or to obtain a wastewater characterization profilethat can be subsequently used to modulate operating parameters of thecontrolled irrigation system. Examples of characteristics of thewastewater can include for instance and without being limitative, COD,BOD₅, TSS, TN, TP, pH, and concentrations of elements such as Ca, Mg, K,Na, SO₄ and Cl.

In some implementations, obtaining the wastewater characterizationprofile can enable to adapt the contaminant loading applied to theirrigation zone. For instance, if it is determined that theconcentration of one or more contaminants of a given wastewater effluentis higher than a predetermined threshold, one parameter that can bemodified is the volume of wastewater applied to the irrigation zone,i.e., the volume of wastewater applied to the irrigation zone can bereduced in accordance with the treatment capacity of the irrigation zoneto reduce the contaminant loading of the irrigation zone. Alternatively,if it is determined that a first wastewater has a concentration of oneor more contaminants that is higher than a predetermined threshold, agiven volume of the first wastewater can be diluted with a secondwastewater having a lower concentration of contaminants to achieve alower overall contaminant loading for the combination of the first andsecond wastewater compared to if the first wastewater was applied alone.

In some implementations, the wastewater can be pre-treated prior tobeing applied to the vegetated land, for instance to reduce theconcentrations of certain contaminants.

Determining whether the wastewater is suitable for application to theirrigation zone can involve obtaining a soil characterization profile.Similarly to what is mentioned above regarding the selection of areas ofthe vegetated land as irrigation zones, obtaining a soilcharacterization profile can include determining a physical propertyand/or a chemical property of a soil sample that is representative ofthe soil in a given irrigation zone. A physical property of a soilsample can include for instance the proportion of sand, silt and/or claycontained in the soil sample, the texture of the soil sample, thecoefficient of uniformity of the soil sample, the coefficient ofcurvature of the soil sample, the bulk density of the soil sample, theporosity of the soil sample, the total available water and the saturatedhydraulic conductivity, among others. A chemical property of the soilsample can include for instance its content in organic matter, itscontent in total organic carbon, and a concentration of elements such asNH₄ ⁺, NOx, P, Al, Fe, Ca, Mg and K, among others. It is to beunderstood that these physical and chemical properties are given asexamples only, and that the properties analyzed as part of thedetermination of the soil characterization profile can vary and beadapted depending on the vegetated land, the wastewater characterizationprofile, and/or the goals that are desired to be achieved by theimplementation of the controlled irrigation system.

In some implementations, the vegetated land can be a confined vegetatedland. A confined vegetated land is one that includes a semi-permeable oran impermeable barrier, such as a geomembrane, that is configured tocontain wastewater from travelling downward into the soil past a certaindepth, or to reach other bodies of water via contaminant migration. Aconfined vegetative land can also be delineated by a berm. In otherimplementations, the vegetated land can be an unconfined vegetated land.Examples of unconfined vegetated land can include a vegetated land canbe provided on a top surface of a former landfill, such as a formerwaste containment area or an abandoned mine site. The type of vegetationgrown on the vegetated land can depend on the characteristics of thevegetated land, i.e., whether the vegetated land is a confined vegetatedland versus an unconfined vegetated land. For instance, when thevegetated land is provided on a top surface of a former landfill, thevegetation can be chosen such that the roots of the plants do not damagethe integrity of the cap of the landfill.

Pumping Station, Control Station and Weather Station

Still referring to FIG. 1 , in the implementation shown, the controlledirrigation system 10 further includes a pumping station 22 that includesat least one pump 24, a control station 26, and a weather station 44.The pump 24 is in fluid communication with the irrigation network 20 viaa supply pipeline 46. The irrigation network 20 includes an irrigationpipeline 28 connected to the pump 24 to transport the wastewater to theirrigation zone(s), and a plurality of sub-pipelines 30, 32.

The irrigation pipeline 28 can have various configurations and be madeof various materials depending on the characteristics and volume ofwastewater to transport to the irrigation zones. In the implementationsshown, the irrigation pipeline 28 is divided into a first sub-pipeline30 and a second sub-pipeline 32, the first sub-pipeline 30 beingconfigured for supplying wastewater to the first irrigation zone 14 andthe second sub-pipeline 32 being configured for supplying wastewater tothe second irrigation zone 16. It is to be understood that the term“pipeline” can refer to a tubing, or any structure enabling thetransport of the wastewater to the irrigation zone.

As mentioned above, the supplying of the wastewater to each of theirrigation zones via corresponding sub-pipelines can facilitatecontrolling the volume of wastewater according to specificcharacteristics of the irrigation zone, and more particularly accordingto the data collected by the monitoring device 42 associated with thatirrigation zone. Although each one of the sub-pipelines 30, 32 areillustrated as a single pipeline in FIG. 1 , it is to be understood thateach sub-pipeline 30, 32 can include one or more ramifications, forinstance to provide uniform irrigation over the surface area of theirrigation zone. The configuration of the sub-pipeline 30, 32 can alsochange depending on the type of irrigation chosen. In someimplementations, the irrigation of wastewater can be performed viasurface irrigation or via underground irrigation. Examples of systemsfor performing surface irrigation include surface drip systems andmicro-sprinkler systems. An example of a system for performingunderground irrigation is a buried drip system. The sub-pipelines 30, 32shown in FIG. 1 are thus illustrated as a single line transporting thewastewater for illustrative purposes only. It is to be understood thatmore than one sub-pipeline can be used to supply a controlled volume ofwastewater to a corresponding irrigation zone, and that a sub-pipelinecan correspond to a surface irrigation system and/or a subsurfaceirrigation system, or any other type of irrigation system.

The pump 24 can be for instance a centrifugal pump, or any othersuitable type of pump. The pump 24 supplies wastewater to the irrigationzone(s) via the irrigation network 20. In some implementations, a singlepump can be provided to supply a controlled volume of wastewater torespective irrigation zones. Alternatively, more than one pump can beprovided, for instance with a pump being provided for a given number ofirrigation zones and for a vegetated land that includes more than thegiven number of irrigation zones.

To prevent water hammers in the irrigation network 20, irrigation valves34 can be opened a certain period of time prior to the starting the pump24, and be closed a certain period of time after the pump 24 is turnedoff.

In some implementations, the pumping station 22 further includes avariable frequency drive (VFD) for controlling the operation of the pump24. The VFD can enable the pump 24 to gradually increase its pressure,which can also contribute to avoid water hammers. The VFD can also beused to modulate the operating flow rate.

In the illustrated implementation, and in-line pressure sensor 36 and aflowmeter 38 are provided as instrumentation for transmittinginformation regarding the wastewater flowing in the irrigation network20.

The flowmeter 38 is configured to measure the flow of wastewater flowingin the irrigation network 20, and indirectly, volumes of irrigatedwastewater and associated contaminant loadings. The flow rate providedby the flowmeter 38, which can be expressed for instance in m³/h, can beconverted to a volume of irrigated wastewater per irrigation event, withvolumes of irrigated water being summed to obtain a total volume ofwastewater applied per day, or per another unit of time, which can beexpressed for instance in m³. The total volume of wastewater applied perday can be a parameter of a predetermined irrigation protocol todetermine whether an additional irrigation event can be initiated ornot. In some implementations, the information provided by the flowmeter38 regarding the flow rate of wastewater circulating in the irrigationnetwork 20 can be used as a safety parameter. For instance, if theflowmeter 38 shows a low flow rate in the irrigation network 20, thiscan be indicative of a clogging at a given location in the irrigationnetwork 20, whereas if the flowmeter shows a high flow rate in theirrigation network 20, this can be indicative of a leak in theirrigation network 20.

The pressure sensor 36 can be installed on the main supply line of theirrigation network 20, i.e., the irrigation pipeline 28, downstream ofthe pump 24, to measure the upstream pressure of the irrigation network20. The pressure sensor 36 can be used to monitor the hydraulicproperties of the irrigation network 20. In some implementations, thepressure of the irrigation network 20 provided by the pressure sensorcan act as a safety parameter, with the pump 24 ceasing its action ifthe pressure is above a given pressure threshold, which could indicateleakage in the irrigation network 20, and if the pressure is below agiven pressure threshold, which could indicate clogging in theirrigation network 20.

Although one pressure sensor 36 and one flowmeter 38 are illustrated inFIG. 1 , it is to be understood that one or more additional pressuresensor and/or one or more additional flowmeter can be provided at otherkey locations in the irrigation network 20 to provide furtherinformation on the performance of the irrigation process. For instance,a pressure sensor and/or a flowmeter can be provided on each one of thesub-pipelines of the irrigation network 20. In other implementations,either one of the pressure sensor and the flowmeter, or both, can beomitted.

Each one of the sub-pipelines 30, 32 can be provided with an irrigationvalve 34 provided upstream of a given one of the irrigation zones 14,16, the irrigation valve 34 being configured to be controlled tomodulate the volume of wastewater supplied to the given one of theirrigation zones 14, 16. Each one of the sub-pipelines 30, 32 can alsobe provided with a flushing valve 40 located downstream of a givenirrigation zone and that can be controlled to implement a flushing cyclein the given one of the irrigation zones 14, 16 to clean given portionsof the irrigation network 20. In some implementations, a flushing cyclecan involve simultaneously opening the irrigation valve 34 and theflushing valve 40 of a given irrigation zone to circulate wastewater, orwater from another source, in the corresponding sub-pipeline 30, 32 andin a flushing pipeline 48. To maintain the hydraulic system clean, aflushing cycle can be automatically programed at a specified frequency.In some implementations, an irrigation event can be initiated when theirrigation valve 34 is in an open configuration while the flushing valve40 is in a closed configuration.

The weather station 44 can include various types of weather monitoringinstruments to monitor variables related to meteorological conditions.Examples of monitoring instruments include a temperature sensor, ahumidity sensor, a rain gauge, a solar radiation probe and ananemometer. These weather monitoring instruments can be configured tomeasure and report outdoor temperature, relative humidity, solarradiation, rainfall intensity and volumes, and wind speed, respectively,which are meteorological conditions that can influence the transpirationof the vegetation of the vegetated land. In some implementations, theweather monitoring instruments can be configured to continuously monitormeteorological conditions.

In some implementations, the rain gauge can be a key element of theweather station, since it can provide information relative to therainfall intensity. The rainfall intensity, which can be expressed forinstance in mm/hr, can be a variable that is taken into consideration ina predetermined irrigation protocol, as the rainfall intensity caninfluence the maximum daily volume of wastewater applied to theirrigation zone, or irrigation volume threshold. For instance, in someimplementations, more rain may mean that less wastewater can be appliedto the irrigation, while less rain may mean that more wastewater can beapplied to the irrigation zone.

The control station 26 includes a controller, which can be for instancea programmable logic controller (PLC). The controller can enablecontrolled irrigation of an irrigation zone of a vegetated land. In someimplementations, the controller can enable controlled irrigation of aplurality of irrigation zones, with each irrigation zone being equippedto be irrigated independently from other irrigation zones.

In some implementations, the control station 26 may include a processor.Of note, the processor can be implemented as a single unit (i.e., asingle processor) or as a plurality of interconnected processingsub-units (i.e., a plurality of processors). The processing unit can beembodied by a computer, a microprocessor, a microcontroller, a centralprocessing unit, or by any other type of processing resource (or anycombinations thereof) configured to operate collectively as a processingunit. The processor can be implemented in hardware, software, firmware,or any combination thereof, and be connected to the various componentsof the controlled irrigation system 10 via appropriate communicationports.

At least one component of the control station 26 (e.g., the controlleror the processor) is in data communication with at least one of the pump24, the pressure sensor 36, the flowmeter 38, other component(s),instrument(s) or device(s) of the pumping station 22 if any, themonitoring device 42 or the weather station 44. It should be noted thatthe expression “data communication” may refer to any type of directconnection and/or indirect connection. For example, the controller orthe processor(s) of the control station 26 may be connected to the pump24, the pressure sensor 36, the flowmeter 38, the monitoring device 42and/or the weather station 44 through direct communication such as awired connection or via a network allowing data communication betweendevices or components of a network capable of receiving and/or sendingdata, which may include, to name a few, publicly accessible networks oflinked networks, possibly operated by various distinct parties, such asthe Internet, private networks (PN), personal area networks (PAN), localarea networks (LAN), wide area networks (WAN), cable networks, satellitenetworks, cellular telephone networks and the like, or any combinationsthereof.

The controller is configured to collect data from the instruments of thepumping station 22, which in the scenario illustrated in FIG. 1 includesthe flowmeter 38 and the pressure sensor 36, from the monitoring devices42 distributed over the irrigation zones of the vegetated land, and/orfrom the weather monitoring instruments of the weather station 44. Thecontroller is further configured to analyze the collected data againstpredetermined parameters of a predetermined irrigation protocol todetermine whether an irrigation event can be initiated or not. Forinstance, the controller can collect data related to the volume ofirrigated wastewater supplied to the irrigation zones per irrigationevent, and can sum this data to obtain a total volume of wastewaterapplied per day, or per another unit of time, which is information thatcan then be used to determine whether an irrigation event can beinitiated or not. The rainfall intensity in a period of time prior toinitiation of an irrigation event is also a valuable information todetermine whether an irrigation event can be initiated or not. Inaddition, in some implementations, the forecasted rainfall intensity,which can be determined according to a weather forecast, predicted for agiven period of time prior to initiation of a desired irrigation event,can also be used to determine whether an irrigation event can beinitiated or not. The soil moisture of the irrigation zone, which can beprovided by the monitoring devices installed in the irrigation zone, canalso be used to determine whether an irrigation event can be initiatedor not, as will be discussed in detail below.

The controller (or processor) of the control station 26 is furtherconfigured to process different types of signals, such as the ones thatcan be generated or produced by the pumping station 22 (or componentsthereof, such as the pressure sensor 36 and/or the flowmeter 38), theweather station 44 (or instruments thereof) and/or the monitoring device42. Examples of processing techniques that may be performed by thecontroller may include filtering the signals, performing differentoperations (e.g., additions, subtractions, ratio calculations, Fouriertransforms, filtering, averaging, or any other mathematical functions,transformations and/or analyses) and/or analyzing the signals. Inaddition, the controller of the control station 26 may be configured tocontrol the operation of the components of the controlled irrigationsystem 10.

Once the data has been analyzed by the controller, the controller cansubsequently provide instructions to the pump 24, the irrigation valves34 and the flushing valves 40, to control irrigation of the irrigationzones 14, 16. The controller is thus operatively connected to the pump24, and the pump 24 can receive instructions from the controller tocontrol its operation.

In some implementations, the controlled irrigation system 10 may includea memory, or may include or be connected to a database to store datacollected from the instruments and/or other relevant data. The memorymay be integrated to the controller of the control station 26 or mayalternatively be in data communication with at least one component ofthe control station 26. The data collected by the instruments may bestored in a dataset including information such as measurements orstatistics. Of note, the information stored in the dataset may berepresentative of a past irrigation status of the irrigation zone, anactual (or ongoing) irrigation status of the irrigation, a forecastedirrigation status of the irrigation zone and/or any other relevantindicators or parameters that may be useful to control the irrigation ofwastewater onto the vegetated land. The dataset may be stored as arelational database and may have a database format commonly used in theart, such as Domino, SQL, SCSV, Office 365, or the like. The dataset maycomprise textual information, numeral information, time information,date information, image information, and any combinations thereof.

In some implementations, the memory or the database may further storecalibration data. The calibration data may be representative of controlparameters of the components or instruments of the controlled irrigationsystem 10. The data collected by the instruments may be compared to thecalibration data, and after the comparison, the collected data and thecalibration data may be combined to determine the appropriate controlparameters of at least one of the components or instruments of thecontrolled irrigation system 10. The combination of the collected dataand the calibration data may include an estimation, an approximation, aninterpolation or an extrapolation of the control parameters.

The controller can be further configured to send the data collected fromthe instruments toward the memory, and/or to send the data to a webplatform or a cloud-based platform. Storing collected data related tothe operation of a controlled irrigation system 10 as described hereincan enable characterizing the effect of meteorological conditions andirrigation events on the performance of the controlled irrigation system10.

The controlled irrigation system 10 may include a user interfaceconfigured to control the controlled irrigation system 10 through thecontrol station 26. The user interface may be configured to select oneof the components of the controlled irrigation system 10, receive datacollected by the instruments or components of the controlled irrigationsystem 10 and/or send instructions to the instruments or components ofthe controlled irrigation system 10. The user interface may be in datacommunication with each component of the controlled irrigation system 10through a corresponding communication channel.

In some implementations, the user interface may be a graphical userinterface. As the user interface is operatively connected to at leastone component of the controlled irrigation system 10, a user mayinteract with the controlled irrigation system 10 (or componentsthereof). The user interface may be displayed on a display or a screen.In some implementations, the graphical user interface may be part of aweb-based application that may be accessed and displayed using acomputing device connected to the Internet or any types of network.

The user interface may be configured to provide a visual representationof the controlled irrigation system 10, the control parameters of thecomponents or instruments of the controlled irrigation system, the datacollected by the components or instruments of the controlled irrigationsystem, and/or the calibration data. The visual representation mayinclude other information relevant to control the irrigation of anirrigation zone with wastewater. It should be noted that, in someimplementations, the visual representation may be provided in real-timeor near real-time.

In some implementations, a plurality of functionalities and/or modulableparameters may be accessible through the user interface. The userinterface may be configured to provide an indication of the state of thecontrolled irrigation system 10 through visual inspection of the userinterface and to allow manual control of at least one component orinstrument of the controlled irrigation system 10. For example, andwithout being limitative, the user interface may provide information onzone activity (e.g., idle, irrigating, flushing, soaking, soakingtension low and deactivated), the state of valves (i.e., on or off), thestate of pumps (i.e., on or off), daily irrigated volume per zone,sensor live readings, flowmeter measurements (e.g., flow rate (m³/h))and irrigated volume per zone per day (m³), pressure gauge measurements(e.g., pressure (PSI)), tipping bucket (e.g., rainfall (mm/h) and totalrain (mm/d)) and tensiometers or soil moisture sensors measurements(e.g., tension (kPa)/moisture (%) and limit tension). In addition, theuser interface may be configured to select an irrigation program orprotocol and operate the controlled irrigation system 10 in a manualmode. In the manual mode, a user may activate and/or deactivate anirrigation zone, a valve and/or a pump by interacting with the userinterface.

The control station 26 (or at least one component thereof, e.g., thecontroller or processor) may be part of a programmable computer.Alternatively, the control station 26 may be in data communication withsuch a programmable computer. A programmable computer generally includesat least a processor and a data storage system that may include volatileand non-volatile memory and/or storage elements. The programmablecomputer may be a programmable logic unit, a mainframe computer, server,a personal computer, a cloud-based platform, program or system, laptop,personal data assistance, cellular telephone, smartphone, wearabledevice, tablet device, virtual reality devices, smart display devices,set-top box, video game console, portable video game devices, or virtualreality device. At least one of the steps of the processes describedherein can be implemented in a computer software or program executableby the programmable computer. Of note, computer software or programs maybe implemented in a high-level procedural or object-oriented programmingand/or scripting language to communicate with a computer system. Theprograms can alternatively be implemented in assembly or machinelanguage, if desired. In these implementations, the language may be acompiled or interpreted language. The computer programs are generallystored on a storage media or a device readable by a general or specialpurpose programmable computer for configuring and operating the computerwhen the storage media or device is read by the computer to perform theprocesses (or step(s) thereof) described herein.

In some implementations, at least one component or module of thecontrolled irrigation system 10 can be provided as a plug-in. Theexpression “plug-in” as used herein refers to a software componentadding a predetermined feature or functionality to the controlledirrigation system 10. Providing different components or modules asplug-ins can be associated with some benefits, such as, for example andwithout being limitative, adaptability, modularity and flexibility.

As mentioned above, at least one monitoring device is provided perirrigation zone for monitoring a property indicative of an irrigationstatus of the irrigation zone. In some implementations, the monitoringdevice can be a soil tensiometer. A soil tensiometer is configured toprovide a measurement of soil water tension, or soil moisture tension,at the depth of installation. A soil tensiometer typically includes aporous cup and a glass or plastic tube that are initially filled withwater, and a pressure gauge. The soil water tension is measured againsta partial vacuum that is initially created when the soil tensiometer isfirst installed in an unsaturated soil. The soil tension, which can beexpressed in pressure units such as kPa, is an indicator of the energyrequired by the plant to extract water from the soil. As water is pulledout of the soil by the vegetation and evaporation, the soil will absorbwater from the ceramic cup and thus increase the vacuum inside the tube.The higher the suction, the more difficult it is for the plant towithdraw water from the soil. On the other hand, when the soil is nearor above saturation, water can be suctioned in from the soil to theinside of the tube through the ceramic cup, thereby reducing the vacuuminside the tube.

The water content of any particular soil layer can decrease as a resultof soil evaporation, root absorption, or due to water drainage to anadjacent layer. The soil tension at which a soil can hold water againstgravity and below which there is drainage is referred to as the drainedupper limit (DUL), which can also be referred to as field capacity. Inother words, the DUL can be defined as representing the amount of waterthat remains in the soil and that is available to the vegetation foruptake, after excess water has drained away by gravitational drainageand the rate of change of water content in the soil remains relativelyconstant, indicating that drainage has become negligible. The DUL canthus be viewed as a water content, expressed in volume percentage,remaining in the soil after an irrigation event or a rainfall event, ata given depth and after a given period of time. As mentioned above, theDUL can also be expressed as a soil tension, for instance in kPa, atwhich it is determined that water is retained after gravitational flow.The difference between soil tension and the DUL can thus providevaluable information with respect to the available water reserve of asoil and its capacity to receive more water before witnessinggravitational flow, and in the context of the present description, to besubjected to an irrigation event.

The DUL can be dependent on soil characteristics, such as the soiltexture, structure, and composition, for instance with respect to thepresence of clay, sand, organic matter, etc., the temperature andevapotranspiration.

The DUL can be determined during a startup phase of the implementationof the controlled irrigation system, and be subsequently used as aDUL-related criterion in a predetermined irrigation protocol.Determining the DUL can involve analyzing measurements collected by thetensiometers installed in the irrigation zones following an irrigationevent and/or a rainfall event, or a series of irrigation events and/orrainfall events. The determination of the DUL can thus be performedfollowing the occurrence of a planned irrigation event, or aftersufficient rainfall has been received to fill the soil down to a givendepth, or a combination both.

In some implementations, the DUL can be determined by analysing theevolution of the water tension, given by tensiometers, following anirrigation or rainfall event that saturates the soil at a depth beyondthe measuring point of the tensiometer. At saturation, the measuredtension will be expected to be at its lowest (theoretical zero kPa) and,therefore, under the DUL. Once the irrigation or rainfall event hasstopped, the tension will typically start to increase as the water isleaving the soil profile. When the tension is below the DUL, the waterin the soil will drain by gravity which will be categorized by a steepwater tension curve. The slope (derivative) of the curve will thengradually tend towards zero as the water in the soil is slower andslower to leave the soil. The DUL can be determined by a sudden decreasein the steepness of the curve in the span of a couple hours. Thisvariation in the curve can show the moment when the last of the gravityflowing water leaves the soil profile. The tension corresponding to thewater left in the soil at that point can be interpreted as correspondingto the DUL. Theoretically, when the matric potential of the soil reachesa value of about 0 kPa, there is no longer any suction in the soil, andthe soil can thus be considered saturated. It is to be noted that, inthe context of the present description, the expressions “soil tension”,“soil water tension” and “matric potential” can be used interchangeably.In such a scenario, the pores of the soil can be considered filled withwater and thus, there is no more presence of air in the pores of thesoil. In some implementations, the soil can be considered saturated atvalues higher than 0 kPa, depending on factors such as the calibrationand sensitivity of the tensiometers used to perform the measurements.For instance, in some implementations, the soil can be consideredsaturated when the soil tension reaches a value under 5 kPa.

Thus, in some implementations, determining the DUL can include obtaininga series of soil water tension measurements on the vegetated land duringa startup phase, which can be performed during a series of characterizedevents such as a planned irrigation event or a rainfall event.Determining the DUL can also include characterizing a soil sample fromthe irrigation zone during the startup phase to obtain characteristicsof the soil sample. Once the DUL is obtained for a given irrigationzone, this value can be used as a basis to establish a criterion, i.e.,a DUL-related criterion, against which to compare soil water tensionmeasurements obtained at a given time for a given irrigation zone todetermine if an irrigation event can be initiated. In someimplementations, the DUL-related criterion can be the DUL itself, oralternatively, the DUL-related criterion can be established based on theDUL, as will be described in more detail below.

In some implementations, the DUL can be assessed at given timepoints oraccording to predetermined time intervals once the implementation of thecontrolled irrigation system has been initiated. Assessing the DUL atgiven timepoints or according to predetermined time intervals can enableadjusting certain parameters of operation of the controlled irrigationsystem in response to variations in the measured DUL through time, orcan contribute to validating that the DUL determined during the startupphase remains representation of the soil of the irrigation zone.

Soil water tension measurements indicative of the irrigation status ofthe irrigation zone can be obtained using the one or more soiltensiometers installed in the irrigation zone as the monitoring devices,and can be used to control the irrigation of an irrigation zone withwastewater. For instance, in some implementations, one to two soiltensiometers can be installed per irrigation zone for zone areas of onehectare or less. More than two soil tensiometers can be installed forlarger irrigation zones, or when the irrigation zone includesheterogeneous regions. In implementations where more than one soiltensiometers is used in an irrigation zone, the measurements obtained byeach of the soil tensiometers can be averaged, and the average can thenbe used to be evaluated against a given criterion. Ideally, soiltensiometers are installed under conditions that are representative ofthe entire irrigation zone to provide accurate information regarding theirrigation status of the irrigation zone. The depth of installation of asoil tensiometer can depend on the plant species used. Generally, theceramic cup of the soil tensiometer can be installed in the last thirdof the plant root zone depth. When fast-growing shrub willow is chosenas the vegetation chosen for the vegetated land, the depth ofinstallation of the ceramic cup of the soil tensiometers can be betweenabout 20 cm to about 30 cm, for example.

A process for controlling irrigation of wastewater onto a vegetated landwill now be described in further detail. The process can includedetermining a DUL-related criterion of an irrigation zone of thevegetated land. The irrigation zone can then be monitored to assess themoisture level of the soil, and more particularly by measuring a soilwater tension for the irrigation zone, using one or more soiltensiometer. When a single soil tensiometer is installed in anirrigation zone, the soil water tension measurement can be used as is orthrough a function to remove noise if desired. When more than one soiltensiometer is installed in an irrigation zone, an average of the soilwater tension measurements from the soil tensiometers can be calculatedand used as a representative value of the soil water tension of theirrigation zone. The soil water tension measurement can then beevaluated against a DUL-related criterion that has previously beendetermined for that irrigation zone. The step of evaluating the soilwater tension measurement against the DUL-related criterion of theirrigation zone can be performed automatically or manually.

When performed manually, the soil water tension measurement be evaluatedagainst a DUL-related criterion that has previously been determined forthat irrigation zone, and the operation of the pump can be adjusted inaccordance with the extent of the departure from the DUL-relatedcriterion.

When performed automatically, the soil water tension measurement can betransmitted to a controller as described above for analysis. As thecontroller is operatively to the pump via the VFD, the operation of thepump can be adjusted automatically in accordance with the extent of thedeparture from the DUL-related criterion.

In some implementations, the DUL can be used as a basis to establish acriterion against which a soil water tension measurement is evaluatedand that can be used to determine whether an irrigation event can beinitiated or not, i.e., to establish a DUL-related criterion.

For instance, the DUL-related criterion can be established based on theDUL to which is added a certain percentage of the difference between theDUL and the wilting point of the irrigation zone, and in turn, theDUL-related criterion can be used to determine whether an irrigationevent can be initiated or not. In some implementations, the percentageof the difference between the DUL and the wilting point of theirrigation zone can be less than 30%, less than 20%, less than 15%, lessthan 10%, or less than 5%. It is to be noted that the wilting point canalso be referred to as a lower limit of plant available water. For easeof reference, the percentage of the difference between the DUL and thewilting point can be referred to as x % plant available water (PAW), inwhich scenarios the DUL-related criterion can be expressed as DUL+x %PAW. For instance, for a DUL of 10 kPa and a wilting point of 30 kPa,and a DUL-related criterion of DUL+5% PAW, the DUL-related criterionwould correspond to 11 kPa, as 5% of 20 kPa represents 1 kPa. Inimplementations where the DUL-related criterion is DUL+x % PAW, anirrigation event can be initiated for instance if the soil tension isequal to or above DUL+5% PAW, DUL+10% PAW, DUL+15% PAW, DUL+20% PAW, orDUL+30% PAW.

In another example, the DUL-related criterion can be obtained based onthe impact of an irrigation event on the soil tension, the irrigationevent being initiated when the soil tension is at or near the DUL. Inorder to measure the impact of the irrigation event on soil tension, atest irrigation event can be initiated when the soil tension is at avalue close to or at the DUL, for instance when the DUL is between DULand DUL+x kPa. The x kPa value can be for instance between 0.5 kPa and 5kPa. In some implementations, the x kPa value can be about 1 kPa. Thedifference in soil tension before and after the test irrigation event,i.e., the soil tension loss, is then determined, and this value can beused to determine the DUL-related criterion for irrigation. In suchimplementations, the DUL-related criterion thus corresponds to the DULto which is added the impact of the test irrigation event on the soiltension. For example, for an irrigation zone having a DUL of 10 kPa, ifit is determined that after a test irrigation event initiated when thesoil tension was at DUL+1 kPa, the average tension lost after the testirrigation event is 2 kPa, then the criterion could be determined ascorresponding to 12 kPa+/−1 kPa. This DUL-related criterion can varydepending on the irrigation zone as topography and soil properties canvary for each irrigation zone, and on the hydraulic load applied withevery event. In some implementations, the criterion can be betweenDUL+0.2 kPa and DUL+3 kPa, or between DUL+0.2 kPa and DUL+10 kPa, forexample. When the DUL-related criterion is established in accordancewith the technique described above, the value of this criterion can bereferred to as “DUL+1 irrigation event” in the present document. TheDUL-related criterion can be increased by a safety buffer when the datais new or questionable. For instance, the criterion can be increased byup to 20%. In some implementations, the DUL-related criterion can beadjusted, either manually or automatically, if it is observed that anirrigation event results in the soil tension dropping under the DUL.

In some implementations, when the DUL-related criterion used is “DUL+1irrigation event”, the “DUL+1 irrigation event” can be used as a firstDUL-related criterion, and a second DUL-related criterion can be used todetermine whether an irrigation event characterized by an increasedirrigation volume and/or increased irrigation event duration can beinitiated. The second DUL-related criterion can be referred to as “DUL+xirrigation event”, with x corresponding to a number of irrigation eventsand being greater than 1. Of note, x can be an integer number or anumber with a fractional component. For instance, when x=2, theDUL-related criterion would correspond to “DUL+2 irrigation events”,meaning that the DUL-related criterion corresponds to a soil tensionindicating that an irrigation event that is greater (due to an increasedvolume and/or increased duration) by a factor 2 can be initiated,compared to when an irrigation event that would be initiated followingthe determination that the soil tension is equal or above the criterion“DUL+1 irrigation event” while not reaching the “DUL+2 irrigationevents” criterion. The use of the second DUL-related criterion can bedesirable to determine when it can be advisable to proceed with agreater irrigation event when this second DUL-related criterion is met.In such implementations, a single and “normal” irrigation event can beinitiated if the soil tension measurement is equal or above the firstDUL-related criterion “DUL+1 irrigation event” and below the secondDUL-related criterion “DUL+x irrigation event”. On the other hand, if itis determined that the soil tension measurement is equal or above thesecond DUL-related criterion “DUL+x irrigation event”, a greaterirrigation event by a factor x can be initiated. In an example scenario,the irrigation volume of an irrigation event can be about 100 m³, andthe “DUL+1 irrigation event” criterion can be 25 kPa, for a DUL of 20kPa. If experiments that were previously conducted determined that thesoil tension threshold to irrigate 300 m³ was 40 kPa, for instancewithout risking deep percolation or runoff, this would mean that the“DUL+3 irrigation event” in that scenario would be 40 kPa. In someimplementations, the use of both “DUL+1 irrigation event” and “DUL+xirrigation event” as criteria to determine whether an irrigation evencan be initiated and the increased magnitude of this irrigation eventcan contribute to reducing the effect of gravitational flow in pipelineson the heterogeneity of irrigation in irregular fields, since the longerthe irrigation event, the smaller the effect of post-irrigationgravitational flow may be on the uniformity of the distribution of theirrigated wastewater.

In some implementations, it may be desirable to maintain the soiltension of a given irrigation zone within a certain range to contributeto maximize, or enhance, the volume of wastewater applied to theirrigation zone over time. For instance, when the DUL-related criterionis distinct from the DUL itself, the range can be defined between theDUL and the DUL-related criterion. In some implementations, the rangewithin which to maintain the soil tension can thus correspond to the DULand DUL+x % PAW. In other implementations, the range within which tomaintain the soil tension can correspond to the DUL and DUL+1 irrigationevent, or the DUL and DUL+x irrigation event.

Basing the decision to initiate an irrigation event at least in part onthe soil water tension evaluated against a DUL-related criterion of theirrigation zone can enable the plants and soil to be constantly suppliedwith a volume of wastewater that they can manage, which can contributeto maximizing, or enhancing, the volume of wastewater applied to theirrigation zone over time. Furthermore, basing the decision to initiatean irrigation event at least in part on the soil water tension evaluatedagainst the DUL-related criterion of the irrigation zone also takesadvantage of the soil characteristics and evapotranspiration profile ofthe vegetation to use the ability of the soil and vegetation to receiveand treat the wastewater closest to their full potential. With thisapproach, an objective is to provide a volume wastewater to theirrigation zone per unit of time that is as high as possible to treatlarge volumes of wastewater, while ensuring that the volume of irrigatedwastewater is not so large that untreated wastewater percolates past acertain depth or that the irrigation zone gets flooded.

Thus, providing a controlled irrigation of an irrigation zone so as tomaintain the soil water tension close to the DUL, such as within oneirrigation event of the DUL, i.e., within DUL+1 irrigation event, cancontribute to maximize the amount of water in the field while minimizingdrainage out of the root zone of plants, which in turn can contribute toenhance consumption and evapotranspiration by plants. In addition toenhancing transpiration, maintaining the soil water tension close to theDUL, such as within one irrigation event of the DUL, i.e., within DUL+1irrigation event, can facilitate maintaining a favorable environment inthe root zone to the degradation or the transformation of contaminantsthat can be present in wastewater, such as the degradation of organicmatter, nitrification of ammoniacal nitrogen, etc. By maintaining atension equal or above the DUL, the gravitational flow, i.e.,gravitation drainage, beyond the plants root zone can be avoided, suchthat substantially all of the irrigated wastewater can remain availableto be consumed and transpired by plants.

This strategy contrasts with conventional irrigation approaches used inagriculture. Conventional irrigation approaches used in agriculture aretypically aimed at maximizing yield by minimizing the amount of waterirrigated in the field in order to conserve water resources. Water isthus supplied minimally, i.e., in the least amount, to agriculturalcrops to maintain the soil tension below the wilting point, whichcorresponds to the amount of water in the soil that is held so tightlyby the soil matrix that the roots cannot withdrawn and absorb thiswater, before water stress adversely impacts the plant while ensuringthat yield is not compromised. Conventional irrigation typically startsonly when the crops are near their wilting point (hydraulic stresspoint). The mindset for such conventional approaches is to irrigate onlyif needed, and the volume of water applied per irrigation eventcorresponds to the volume needed to reach the DUL.

Another benefit of using a soil tensiometers to measure the soil watertension in the soil of the irrigation zone is that such soil watertension measurements are not impacted by the salt content of waterpresent in the pores of the soil. Given that wastewater can have a highsalt content or a variable salt content, the use of soil water tensionmeasurements to provide information of the irrigation status of anirrigation zone independently of the salt content of the wastewater canthus enable to have access to more accurate and reliable data comparedto “dielectric type” soil moisture probes typically used in agricultureapplications.

In some implementations, soil water tension measurements can be takenfor each one of the irrigation zones, and the controlled irrigationprocess can include determining the irrigation zone with the largestdeparture, or largest differential, above the corresponding DUL-relatedcriterion. Once the irrigation zone having the largest differential ofthe soil water tension measurement above the DUL-related criterion isdetermined, the controller can be configured to send instructions to thepump to initiate an irrigation event for that given irrigation zone.Depending on the configuration of the irrigation network, an irrigationevent can be initiated for more than one irrigation zone at a time, orsimultaneously, for instance for the irrigation zones having the largestdifferential the corresponding soil water tension measurement and thecorresponding DUL-related criterion. Alternatively, the irrigationnetwork can be configured to irrigate irrigation zones sequentially,starting by irrigating a first irrigation zone having the largestdifferential between the corresponding soil water tension measurementand the corresponding DUL-related criterion, followed by irrigating asecond irrigation zone having the second largest differential betweenthe corresponding soil water tension measurement and the correspondingDUL-related criterion, and so on.

Controlled Application of Wastewater to an Irrigation Zone of aVegetated Land by Implementation of a Predetermined Irrigation Protocol

With reference now to FIGS. 2-6 , various implementations of apredetermined irrigation protocol for controlling the application ofwastewater to an irrigation will now be described.

In general terms, a main objective of the irrigation protocol is toapply a high daily hydraulic loading to each irrigation zone. Theexpression “hydraulic loading” refers to the volume of wastewaterapplied to an irrigation zone per time period, with a daily hydraulicloading representing the total volume of wastewater applied per day.

It is to be noted that the expression “irrigation protocol” can be usedinterchangeably with the expressions “control loop” and “irrigationfeedback loop”, as the irrigation protocol involves the generation ofdata by the weather station, the weather monitoring device(s), and/orthe monitoring devices installed in the irrigation zones, and additionalmonitoring devices such as hydraulic monitoring devices including forinstance a flowmeter, a pressure gauge, a real time clock etc., with thecontroller collecting such data, analyzing it, and generating outputdata that can be used as instructions for operating components of theirrigation network, such as the pump, the irrigation valves and theflushing valves.

The irrigation protocol can be established using various parameters thatrelate to the physicochemical characteristic of the wastewater that isto be applied to the irrigation zones, i.e., the wastewatercharacterization profile, the soil characterization profiles of theirrigation zones, including the soil water tension of the irrigationzones. The term “parameter”, when referring to an irrigation protocol asdescribed herein, can be used interchangeably with the terms conditionor criterion.

FIG. 2 illustrates an example of an irrigation protocol that includesseven parameters that can influence whether an irrigation event having astart irrigation time and an end irrigation time can be initiated. Theseseven parameters are:

-   -   an irrigation schedule corresponding to a time period during        which irrigation is determined to be indicated;    -   a forecasted rainfall intensity;    -   a soaking time;    -   an irrigation volume threshold or maximum daily irrigation        volume;    -   a rainfall intensity prior to the irrigation event;    -   a soil moisture; and    -   an irrigation event duration.

Each of these parameters will be described in the following paragraphs.It is to be noted that a given irrigation protocol generally includes atleast the irrigation schedule and the irrigation duration as parameters,and a selection of at least one of the prior irrigation time, the totaldaily irrigated volume, the forecasted rainfall intensity, the rainfallintensity, and the soil moisture. It should thus be understood that whenusing the expression “if all other criteria of the irrigation protocolare met” in the below paragraphs, the number of parameters or criteriacan vary according to the chosen protocol.

Irrigation Schedule

The irrigation schedule corresponds to an interval of time during a24-hour period during which it has been previously established thatinitiating an irrigation event is suitable. The irrigation schedule hasa start time and an end time. In some implementations, the irrigationschedule can correspond to the photoperiod at the given time in theyear. The photoperiod can be defined as the period of time during theday between the sunrise and the sunset, and thus can vary over thecourse of the year. Performing an irrigation event during thephotoperiod can promote evaporation on soil and plants surfaces viaexposition to solar radiation. This practice of maximizing water loss istypically contrary to the good practice of conventional agriculturalirrigation where one seeks to minimize water loss. The range of hourswhere irrigation can be initiated, i.e., the irrigation schedule, can beautomatically adjusted throughout the year, or the period of the yearwhen irrigation is possible depending on the climate, with the data fromthe solar radiation sensor of the weather station to take into accountvariations in the photoperiod. The irrigation schedule can also beadjusted to start a given number of minutes before the sunrise, and/orto end a given number of minutes after the sunset. In otherimplementations, the irrigation schedule can be manually adjustedaccording to other factors such as the availability of wastewater to betreated.

As an example, an irrigation schedule in June in the NorthernHemisphere, can be between 6h00 and 20h00. Thus, no irrigation eventwould be initiated if the time of day is outside that range of time,whereas if the time of day falls within that range, an irrigation eventcan be initiated, if all other criteria of the irrigation protocol aremet.

Forecasted Rainfall Intensity

The forecasted rainfall intensity is defined as the amount of rainexpected to fall during a given period of time, the given period of timeoccurring before a given timepoint. The forecasted rainfall intensitycan be expressed in depth units per unit of time, such as mm per hour(mm/h), and the given timepoint can be expressed in unit of time, suchas in minutes (min).

Including the forecasted rainfall intensity in the irrigation protocolcan facilitate avoiding risks of wastewater runoff and percolationbeyond the plant root zone by anticipating events that could lead tosuch risks.

In some implementations, no irrigation event is initiated if it isexpected to rain with an intensity greater than x mm/h in less than agiven number of minutes, whereas an irrigation event can be initiated ifthe forecasted rainfall intensity is expected to be equal to x (or bebelow x if x does not correspond to zero) for the next given number ofminutes.

For example, x can correspond to zero, such that no irrigation event isinitiated if it is expected to rain with an intensity greater than zeromm/h in less than a given number of minutes, whereas an irrigation eventcan be initiated if the forecasted rainfall intensity is expected to bezero for the next given number of minutes.

In some implementations, the criteria associated with the forecastedrainfall intensity can be adjusted to values greater than zero mm/hdepending on the characteristics of the wastewater effluent, and/or theenvironmental risks associated with a potential runoff and percolationof the wastewater effluent. For instance, for wastewater effluents thatare considered less contaminated, it may be acceptable to allow theforecasted rainfall intensity to be greater than zero. Thus, in someimplementations, the forecasted rainfall intensity above which noirrigation event is initiated can range for instance between about 0.2mm/h to about 10 mm/h, at anytime in a number of minutes that can rangebetween 15 and 90 minutes. It is to be understood that these values aregiven for exemplary purposes only and should not be consideredlimitative.

Soaking Time

The soaking time corresponds to the time elapsed between two successiveirrigation events in the same irrigation zone, i.e., the delay betweentwo irrigation events in a same irrigation zone. The soaking time can bedetermined according to a period of time that is sufficient for thewastewater supplied to the irrigation zone to percolate through the soilmatrix and reach the monitoring device measuring soil properties, suchas soil tensiometers, so as to enable the monitoring device to analyzethe soil conditions before a subsequent irrigation event is initiated.The soaking time is dependent on soil characteristics, and can bedetermined on site during a startup phase of the implementation of thecontrolled irrigation system. In some implementations, soil tensiometerscan be used to determine the soaking time of an irrigation zone, toevaluate the progression through time of the soil water tensionfollowing a planned irrigation event and/or a rainfall event. In someimplementations, the soaking time could be reassessed in an automatedfashion during system operation, for example by considering the time ittakes for a tensiometer reading of a soil with a given matric potentialto respond to a given irrigation event.

As an example, in some implementations, the soaking time can range frombetween about 2 minutes to about 30 minutes. For example, if a soakingtime is set at 5 minutes, and the prior irrigation event finished at13h05, i.e., the prior irrigation time is 13h05, a subsequent irrigationevent would not be initiated before 13h10, if all other criteria of theirrigation protocol are met.

Irrigation Volume Threshold or Maximum Daily Irrigation Volume

The irrigation threshold, or maximum daily irrigation volume perirrigation zone, refers to a predetermined cumulative volume ofwastewater that has been determined to be suitable to apply to anirrigation zone per a given period of time, such as per day.

The maximum daily irrigation volume can be determined in accordance withthe wastewater characterization profile, and thus can vary depending onthe concentration of contaminants in the wastewater. The determinationof maximum daily irrigation volume in accordance with wastewatercharacterization profile can enable ensuring that the contaminant loadapplied to the irrigation zone does not exceed the capacity of the soil,the microorganisms and the vegetation to receive such wastewater, anddegrade, transform, adsorb or absorb the contaminants. The maximum dailyirrigation volume can thus depend on the nature of the wastewater to betreated, and can vary over time. Furthermore, the maximum dailyirrigation volume can also depend on the soil characterization profile,and on the characteristics of the vegetation of the vegetated land, suchas the vegetation transpiration.

When using the term “maximum” or “maximizing” in the context of thepresent description, it is to be understood that it is intended to referto a volume that tends toward what has been previously determined tocorrespond to a theoretical volume or empirical volume of wastewaterthat is suitable to supply to a given irrigation zone during a givenperiod of time, and can include variations to such volumes of wastewaterthat are up to 10% of the previously determined theoretical volume orempirical volume.

It is also to be noted that the expression “maximum daily irrigationvolume” can be used interchangeably with the expressions “cumulativedaily irrigation volume threshold”, “daily irrigation volume threshold”,and “irrigation volume threshold”.

In some implementations, when the wastewater effluent is loaded withorganic matter and/or ammoniacal nitrogen, determining the wastewatercharacterization profile can include carrying out an oxygen balanceduring a startup phase of the implementation of the controlledirrigation system to compare the daily biological oxygen demand loadingassociated to the irrigation to the daily soil passive oxygenationcapacity.

In some implementations, when the wastewater effluent is loaded withmetals or nutrients, determining the wastewater characterization profilecan include analyzing the contaminant loading of the wastewater, and themaximum daily irrigation volume can be determined by comparing thecontaminant loading applied to an irrigation zone with the quantity ofcontaminants that can be absorbed by the vegetation. Taking intoconsideration the contaminant loading of the wastewater contributes tomaintain treatment efficiency and process durability, for instance byreducing the risk of soil clogging due a contaminant overload, which arebenefits over conventional irrigation systems.

Once the maximum daily irrigation volume per irrigation zone is reached,a subsequent irrigation event would not be initiated. An irrigationevent can be initiated if the maximum daily irrigation volume perirrigation zone is not met, and if all other criteria of the irrigationprotocol are met.

Rainfall Intensity

The rainfall intensity is defined as the ratio of the total amount ofrain falling during a given period to the duration of the period. Therainfall intensity can be expressed in depth units per unit time, suchas mm per hour (mm/h).

Including the rainfall intensity in the irrigation protocol canfacilitate avoiding risks of wastewater runoff and percolation beyondthe plant root zone.

In some implementations, no irrigation event is initiated when therainfall intensity is greater than zero mm/h, and an irrigation eventcan be initiated when the rainfall intensity is equal to zero mm/h.

In some implementations, the criterion associated with the rainfallintensity can be adjusted to a value greater than zero depending on thenature of the wastewater effluent and the wastewater characterizationprofile, and/or on the environmental risks associated with a potentialrunoff and percolation of the wastewater. For instance, in someimplementations, the rainfall intensity above which no irrigation eventis initiated can range between about 0.2 mm/h to about 2 mm/h, orbetween about 0.2 mm/h to about 10 mm/h.

In some implementations, the controller can be configured to take intoaccount the rainfall weather forecast, and the irrigation protocol canbe adapted such that no irrigation event is initiated if it is supposedto rain in the next given number of minutes, whereas an irrigation eventcan be initiated if no rain is expected for the next given number ofminutes.

Soil Moisture

The soil moisture refers to the water stored in the soil, and can beaffected by the characteristics of the soil and the rainfall events, andcan be monitored using monitoring devices distributed over theirrigation zones.

In some implementations and as mentioned above, the monitoring devicecan include a soil tensiometer to measure soil water tension. Using soilwater tension can be advantageous to evaluate soil moistureindependently of the salinity of the wastewater used for irrigating theirrigation zone.

The soil moisture allows the system to irrigate when the soil is readyto receive more wastewater, which decreases the risks of wastewaterdrainage and runoff.

When the soil moisture is evaluated using one or more soil tensiometersto obtain soil water tension measurements, the soil water tensionmeasurements collected for a given irrigation zone can be analyzedagainst at least one DUL-related criterion, which can be the DUL itself,or a criterion based on the DUL, for that given irrigation zone. Thecriterion related to the DUL can be a parameter that is set manuallyfollowing the determination of the DUL during the startup phase. Thecriterion related to the DUL can also be reassessed after theimplementation of the controlled irrigation system is initiated.

In some implementations and as described above, the criteria related tothe DUL, i.e., the DUL-related criterion, can correspond to the DUL towhich is added a certain value, which can correspond for instance toless than 30% of the difference between the DUL and the wilting point,or less than 20%, less than 15%, less than 10%, or less than 5% of thedifference between the DUL and the wilting point. As mentioned above,the percentage of the difference between the DUL and the wilting pointcan thus be referred to as x % plant available water (PAW), with theDUL-related criterion being expressed as DUL+x % PAW. In suchimplementations, irrigation can be initiated when the soil water tensionmeasurement is equal or above the DUL+x % PAW, and if all other criteriaof the irrigation protocol are met.

In other implementations, the criterion related to the DUL, i.e., theDUL-related criterion, can correspond to DUL+1 irrigation event. In suchimplementations, irrigation can be initiated when the soil water tensionmeasurement is equal or above the DUL+1 irrigation event, and if allother criteria of the irrigation protocol are met.

When the soil water tension measurements are analyzed against twoDUL-related criteria, the first DUL-related criterion can correspond toDUL+1 irrigation event, and the second DUL-related criterion cancorrespond to DUL+x irrigation event, with x being greater than 1. Insuch implementations, an irrigation event can be initiated when the soilwater tension measurement is equal or above the DUL+1 irrigation eventand below DUL+x irrigation event, and if all other criteria of theirrigation protocol are met. For such irrigation event, the volume ofwastewater applied or the duration of the irrigation event cancorrespond to the one associated with the DUL+1 irrigation event.Furthermore, if the soil water tension measurement is equal or above theDUL+x irrigation event, thus being necessarily above the DUL+1irrigation event, then the magnitude of the irrigation event can be asdetermined by the value of x, x being above 1 and corresponding to amultiplier of the irrigation volume or irrigation duration of theirrigation event associated with the DUL+1 irrigation event. In someimplementations, the DUL+x irrigation event can be used as a standalonecriterion.

In some implementations, the controlled irrigation system 10 may includea prediction module in data communication with the control station 26and the weather station 44. The prediction module can be configured to“learn” or “predict” which weather and field conditions lead to givenchanges in the soil water tension measured in the irrigation zone. Byhaving a better overview of the impact of certain weather conditions onthe soil water tension, at least one of the moment of irrigation event,the irrigation run time, the DUL+1 irrigation event, or the irrigationvolume threshold can also be adapted, to maintain the soil water tensionwithin a certain range relative to the DUL.

The prediction module may be configured to output an estimate of thesoil water tension, or a projected soil water tension, based oninformation representative of the weather conditions. More specifically,the prediction module can receive at least one of the weather conditionsand the actual soil tension as an input(s) and provide an estimatedvalue of the impact of an irrigation event on the soil water tension asan output. The estimation of the soil water tension may also be based ona priori knowledge, computation, empirical data, theoretical model,calibration data and any combinations thereof. The estimated soil watertension may be representative of an instantaneous (i.e., actual) soilwater tension and may be saved or stored on the memory or in thedatabase. It should be noted that the instantaneous estimated watertension value may be temporarily or permanently saved. Subsequent watertension values may then be determined or evaluated, based on thecollection or accumulation of the plurality of successive instantaneousestimated water tension values.

In some implementations, the prediction module may be configured toreceive code, computer-readable instructions or any other computerprogramming steps or sub-steps as inputs and, in response thereto, sendinstructions or requests to the control station 26. These instructionsor requests may be used to alter, modify and/or adjust the irrigation ofthe irrigation zone. Of note, these requests may be manually provided,automatically provided or semi-automatically provided.

Irrigation Duration

The irrigation duration corresponds to the duration of an irrigationevent. The value of this parameter can depend on several factors, suchas the irrigation rate, the availability of the wastewater effluent, thehydraulic configuration of the irrigation network, and the soilcharacterization profile.

The irrigation duration can be balanced between a duration that is tooshort, which may not be efficient from a hydraulic point of view and forthe uniformity of the irrigation event, and a duration that is too long,which may lead to a risk of overshooting the irrigation.

In the context of the controlled irrigation system as described herein,the irrigation hydraulic loading per irrigation event used in theirrigation protocol can be considered as being substantially smallercompared to values of irrigation hydraulic loading for typicalagricultural operations. It has been found that short but frequentirrigation events can facilitate a precise control of the soil watertension. With this atypical duration and hydraulic loading of irrigationevents, the controlled irrigation system can maintain the soil watertension close to the DUL, which can be considered as an optimal tensionfor wastewater treatment, without exceeding it, i.e., without saturatingthe soil and loosing water to gravity. For example, in someimplementations, the irrigation duration can be between 5 minutes and 30minutes, the hydraulic rate can be between about 1 mm and about 5 mm perevent and is repeated between 0 and 30 times over the period of 24hours. This type of irrigation schedule can enable applying a volume ofwastewater per irrigation event that contributes to maintaining the soilwater tension close to the DUL, or above the DUL such as for instance atDUL+x % PAW (with x % being less than 30%) or at DUL+1 irrigation event,or within an interval defined by DUL and DUL+x % PAW (with x % beingless than 30%), or DUL and DUL+1 irrigation event, which in turn cancontribute to maximize the amount of the wastewater applied to thevegetated land over time.

In contrast, conventional irrigation typically starts only when the soilmoisture reaches a percentage of the total available water capacity, orplant available water, that is typically above 50% from the DUL. Theprinciple is to irrigate only if plants become in need of water. In suchconventional irrigation processes, the volume of water applied perirrigation event typically corresponds to the volume needed to reach theDUL from a percentage of the total available water capacity that istypically above 50% from the DUL, such that typical hydraulic rate inconventional agricultural applications can be between 10 mm and 50 mmper event and irrigation occurs only every couple of days.

In some implementations, the duration of the irrigation event can bedetermined at least in part so as to maintain the soil tension close tothe DUL, or above the DUL such as for instance at DUL+x % PAW (with x %being less than 30%) or at DUL+1 irrigation event, or within theinterval defined by DUL and DUL+x % PAW (with x % being less than 30%),or DUL and DUL+1 irrigation event.

Examples of Irrigation Protocol Implementations and Associated ControlLoop

Referring now to FIG. 2 , in some implementations, the irrigationprotocol can include the seven of the parameters described above. Insuch implementations, the controller can be configured to maintain theoperation of the pump and associated irrigation network in standby, suchthat no irrigation event is initiated, when at least one of:

-   -   the start irrigation time is outside of the irrigation schedule,        which can be interpreted as meaning that the time of the day        evaluated to determine if an irrigation event can be initiated        is outside of the irrigation schedule;    -   the forecasted rainfall intensity is predicted to be above a        forecasted rainfall intensity threshold in less than a given        number of minutes;    -   the prior irrigation time is less than a given number of        minutes, which can be interpreted as meaning that the number of        minutes following the end of the prior irrigation event is less        than a predetermined delay between two successive irrigation        events corresponding to the soaking time;    -   the total daily irrigated volume is equal or above an irrigation        volume threshold, which can be interpreted as meaning that the        total volume of wastewater that has been applied to the        irrigation zone to date, starting at the beginning of the        irrigation schedule, has reached the irrigation volume threshold        volume of wastewater per day that the irrigation zone can        receive;    -   the rainfall intensity at the start irrigation time is above a        rainfall intensity threshold, with the rainfall intensity        threshold being set at either zero or above zero; and    -   the soil water tension of the irrigation zone is below a        DUL-related criterion.

Still referring to the implementation shown in FIG. 2 , the controllercan be further configured to operate the pump and associated irrigationnetwork to initiate an irrigation event having a given irrigationduration, when the following criteria are met:

-   -   the start irrigation time is within the irrigation schedule,        which can be interpreted as meaning that the time of the day        evaluated to determine if an irrigation event can be initiated        is within the irrigation schedule;    -   the forecasted rainfall intensity is anticipated to be equal or        below the forecasted rainfall intensity threshold for a given        number of minutes, or the forecasted rainfall intensity is        anticipated to be higher than the forecasted rainfall intensity        threshold but after the given number of minutes;    -   the prior irrigation time is equal to or more than a given        number of minutes, which can be interpreted as meaning that the        number of minutes following the end of the prior irrigation        event is equal or more than the soaking time;    -   the total daily irrigated volume is below irrigation volume        threshold, which can be interpreted as meaning that the total        volume of wastewater that has been applied to the irrigation        zone to date, starting at the beginning of the irrigation        schedule, has not reached the irrigation volume threshold of        wastewater per day that the irrigation zone can receive;    -   the rainfall intensity at the start irrigation time is equal to        or below the rainfall intensity threshold; and    -   the soil water tension of the irrigation zone is equal or above        a DUL-related criterion.

Referring to FIG. 3 , in some implementations, the irrigation protocolcan include six of the parameters described above. In suchimplementations, the controller can be configured to maintain theoperation of the pump and associated irrigation network in standby, suchthat no irrigation event is initiated, when at least one of:

-   -   the start irrigation time is outside of the irrigation schedule,        which can be interpreted as meaning that the time of the day        evaluated to determine if an irrigation event can be initiated        is outside of the irrigation schedule;    -   the prior irrigation time is less than a given number of        minutes, which can be interpreted as meaning that the number of        minutes following the end of the prior irrigation event is less        than a predetermined delay between two successive irrigation        events corresponding to the soaking time;    -   the total daily irrigated volume is equal or above an irrigation        volume threshold, which can be interpreted as meaning that the        total volume of wastewater that has been applied to the        irrigation zone to date, starting at the beginning of the        irrigation schedule, has reached the irrigation volume threshold        volume of wastewater per day that the irrigation zone can        receive;    -   the rainfall intensity at the start irrigation time is above a        rainfall intensity threshold, with the rainfall intensity        threshold being set at either zero or above zero; and    -   the soil water tension of the irrigation zone is below a        DUL-related criterion.

Still referring to the implementation shown in FIG. 3 , the controllercan be further configured to operate the pump and associated irrigationnetwork to initiate an irrigation event having a given irrigationduration, when the following criteria are met:

-   -   the start irrigation time is within the irrigation schedule,        which can be interpreted as meaning that the time of the day        evaluated to determine if an irrigation event can be initiated        is within the irrigation schedule;    -   the prior irrigation time is equal to or more than a given        number of minutes, which can be interpreted as meaning that the        number of minutes following the end of the prior irrigation        event is equal or more than the soaking time;    -   the total daily irrigated volume is below irrigation volume        threshold, which can be interpreted as meaning that the total        volume of wastewater that has been applied to the irrigation        zone to date, starting at the beginning of the irrigation        schedule, has not reached the irrigation volume threshold of        wastewater per day that the irrigation zone can receive;    -   the rainfall intensity at the start irrigation time is equal to        or below the rainfall intensity threshold; and    -   the soil water tension of the irrigation zone is equal or above        a DUL-related criterion.

Referring to FIG. 4 , in some implementations, the irrigation protocolcan include a selection of parameters among the prior irrigation time,the total daily irrigated volume, the rainfall intensity, the forecastedrainfall intensity, and the soil moisture. In the implementation shownin FIG. 4 , the selected parameters include the prior irrigation time,the total daily irrigated volume and the rainfall intensity. In suchimplementations, the controller can be configured to maintain theoperation of the pump and associated irrigation network in standby, suchthat no irrigation event is initiated, when at least one of:

-   -   the start irrigation time is outside of the irrigation schedule;    -   the total daily irrigated volume is equal or above an irrigation        volume threshold;    -   the prior irrigation time is less than a given number of        minutes, which can be interpreted as meaning that the number of        minutes following the end of the prior irrigation event is less        than a predetermined delay between two successive irrigation        events corresponding to the soaking time; and    -   the rainfall intensity at the start irrigation time is above a        rainfall intensity threshold, with the rainfall intensity        threshold being set at either zero or above zero.

Still referring to the implementation shown in FIG. 4 , the controllercan be further configured to operate the pump and associated irrigationnetwork to initiate an irrigation event having a given irrigationduration, when the following criteria are met:

-   -   the start irrigation time is within the irrigation schedule;    -   the prior irrigation time is equal to or more than a given        number of minutes, which can be interpreted as meaning that the        number of minutes following the end of the prior irrigation        event is equal or more than the soaking time;    -   the total daily irrigated volume is below the irrigation volume        threshold; and    -   the rainfall intensity at the start irrigation time is equal to        or below the rainfall intensity threshold.

In the scenario presented in FIG. 4 , no irrigation event is thusinitiated if the irrigation start time is outside the irrigationschedule, the rainfall intensity at the start irrigation time is above arainfall intensity threshold, or if the irrigation volume threshold hasbeen reached, and an irrigation event can be initiated if the startirrigation time is within the irrigation schedule and the irrigationvolume threshold has not been reached, as long as there is no rainfallor the rainfall intensity is equal to or below a certain threshold.

Referring to FIG. 5 , in some implementations, the irrigation protocolcan include a selection of parameters among the prior irrigation time,the total daily irrigated volume, the rainfall intensity, the forecastedrainfall intensity, and the soil moisture. In the implementation shownin FIG. 5 , the selected parameters include the prior irrigation time,the total daily irrigated volume and the soil moisture. In suchimplementations, the controller can be configured to maintain theoperation of the pump and associated irrigation network in standby, suchthat no irrigation event is initiated, when at least one of:

-   -   the start irrigation time is outside of the irrigation schedule;    -   the total daily irrigated volume is equal or above an irrigation        volume threshold;    -   the prior irrigation time is less than a given number of        minutes, which can be interpreted as meaning that the number of        minutes following the end of the prior irrigation event is less        than a predetermined delay between two successive irrigation        events corresponding to the soaking time; and    -   the soil water tension of the irrigation zone is below a        DUL-related criterion.

Still referring to the implementation shown in FIG. 5 , the controllercan be further configured to operate the pump and associated irrigationnetwork to initiate an irrigation event having a given irrigationduration, when the following criteria are met:

-   -   the start irrigation time is within the irrigation schedule;    -   the prior irrigation time is equal to or more than a given        number of minutes, which can be interpreted as meaning that the        number of minutes following the end of the prior irrigation        event is equal or more than the soaking time;    -   the total daily irrigated volume is below the irrigation volume        threshold; and    -   the soil water tension of the irrigation zone is equal or above        a DUL-related criterion.

In the case of the scenario presented in FIG. 5 , no irrigation event isthus initiated if the irrigation start time is outside the irrigationschedule, the soil water tension at the start irrigation time is belowthe DUL-related criterion, or if the irrigation volume threshold hasbeen reached, and an irrigation event can be initiated if the startirrigation time is within the irrigation schedule and the irrigationvolume threshold has not been reached, as long as the soil water tensionof the irrigation zone is equal or above a DUL-related criterion.

In the implementation shown in FIG. 6 , the selected parameter is thetotal daily irrigated volume. In such implementations, the controllercan be configured to maintain the operation of the pump and associatedirrigation network in standby, such that no irrigation event isinitiated, when at least one of:

-   -   the start irrigation time is outside of the irrigation schedule;    -   the prior irrigation time is less than a given number of        minutes, which can be interpreted as meaning that the number of        minutes following the end of the prior irrigation event is less        than a predetermined delay between two successive irrigation        events corresponding to the soaking time; and    -   the total daily irrigated volume is equal to or above an        irrigation volume threshold.

Still referring to the implementation shown in FIG. 6 , the controllercan be further configured to operate the pump and associated irrigationnetwork to initiate an irrigation event having a given irrigationduration, when the following criteria are met:

-   -   the start irrigation time is within the irrigation schedule;    -   the prior irrigation time is equal to or more than a given        number of minutes, which can be interpreted as meaning that the        number of minutes following the end of the prior irrigation        event is equal or more than the soaking time; and    -   the total daily irrigated volume is below the irrigation volume        threshold.

In the case of the scenario presented in FIG. 6 , no irrigation event isinitiated if the irrigation start time is outside the irrigationschedule or if the irrigation volume threshold has been reached, and anirrigation event can be initiated if the irrigation start time is withinthe irrigation schedule and the irrigation volume threshold has not beenreached.

The scenarios illustrated in FIGS. 2-6 are examples of irrigationprotocols that can be implemented to control the irrigation of anirrigation zone. It is to be understood that in other implementations,an irrigation protocol in accordance with the techniques describedherein can include parameters that are different than those exemplifiedabove, or can include additional parameters.

In the scenarios presented above, when the vegetated land includes morethan one irrigation zone and it is desired to irrigate the irrigationzones sequentially rather than simultaneously, the controller can befurther configured to apply an additional criterion to determine thesequence of irrigation of the irrigation zones. In some implementations,the criterion applied can be that the irrigation zone having the largestdifferential of its soil water content measurement above its DUL-relatedcriterion is irrigated first, the irrigation zone having the secondlargest differential of its soil water content measurement above itsDUL-related criterion is irrigated second, etc., until the irrigationzones of the vegetated land have all been irrigated. In someimplementations, the irrigation zones having the largest differentialsof their soil water content measurement above their respectiveDUL-related criterion can be grouped together to be subjected to anirrigation event. Multiple scenarios are thus possible depending on theirrigation protocol chosen and the configuration of the irrigationnetwork.

In accordance with another aspect of the present description, there isprovided a non-transitory computer readable storage medium having storedthereon computer executable instructions that, when executed by aprocessor, cause the controller or processor to perform the methods thathave been previously described. The non-transitory computer storagemedium can be integrated to the systems or assemblies that have beendescribed in the present description. The non-transitory computerstorage medium could otherwise be operatively connected with the systemsor assemblies. In the present description, the terms “computer readablestorage medium” and “computer readable memory” are intended to refer toa non-transitory and tangible computer product that can store andcommunicate executable instructions for the implementation of varioussteps of the method disclosed herein. The computer readable memory canbe any computer data storage device or assembly of such devices,including random-access memory (RAM), dynamic RAM, read-only memory(ROM), magnetic storage devices such as hard disk drives, solid statedrives, floppy disks and magnetic tape, optical storage devices such ascompact discs (CDs or CDROMs), digital video discs (DVD) and Blu-Ray™discs; flash drive memory, and/or other non-transitory memorytechnologies. A plurality of such storage devices may be provided, ascan be understood by those skilled in the art. The computer readablememory may be associated with, coupled to, or included in a computer orprocessor configured to execute instructions contained in a computerprogram stored in the computer readable memory and relating to variousfunctions associated with the computer.

In some implementations, at least one step of the proposed processes ormethods may be implemented as software instructions and algorithms,stored in computer memory and executed by processors. It should beunderstood that computers may be used, in these implementations, toimplement to proposed system, and to execute the proposed method. Inother words, the skilled reader will readily recognize that steps ofvarious above-described processes or methods can be performed byprogrammed computers. In view of the above, some implementations arealso intended to cover program storage devices, e.g., digital datastorage media, which are machine or computer readable and encodemachine-executable or computer-executable programs of instructions,wherein said instructions perform some or all of the steps of saidabove-described methods. The implementations are also intended to covercomputers programmed to perform said steps of the above-describedmethods.

Several alternative implementations and examples have been described andillustrated herein. The implementations of the technology describedabove are intended to be exemplary only. A person of ordinary skill inthe art would appreciate the features of the individual implementations,and the possible combinations and variations of the components. A personof ordinary skill in the art would further appreciate that any of theimplementations could be provided in any combination with the otherimplementations disclosed herein. It is understood that the technologymay be embodied in other specific forms without departing from thecentral characteristics thereof. The present implementations andexamples, therefore, are to be considered in all respects asillustrative and not restrictive, and the technology is not to belimited to the details given herein. Accordingly, while the specificimplementations have been illustrated and described, numerousmodifications come to mind.

The invention claimed is:
 1. A process for controlling irrigation ofwastewater to a vegetated land, comprising: obtaining a soil watertension measurement indicative of an irrigation status in an irrigationzone; wherein when the soil water tension measurement of the irrigationzone is equal to or above a DUL-related criterion, irrigating theirrigation zone with a given volume of wastewater during an irrigationevent having a start irrigation time and an end irrigation time definingan irrigation duration, the given volume of wastewater being determinedso as to maximize an amount of the wastewater applied to the vegetatedland over time.
 2. The process of claim 1, further comprisingdetermining a differential between the soil water tension measurementand the DUL-related criterion, the irrigation duration or the givenvolume of wastewater being adjustable in accordance with thedifferential between the soil water tension measurement and theDUL-related criterion.
 3. The process of claim 1, wherein the irrigationduration or the given volume of wastewater is adjustable to maintain thesoil water tension measurement above the DUL-related criterion.
 4. Theprocess of claim 1, wherein the DUL-related criterion corresponds to aDUL of the irrigation zone.
 5. The process of claim 1, furthercomprising determining the DUL-related criterion, comprising:determining a DUL of the irrigation zone, comprising: obtaining a seriesof soil water tension measurements on the irrigation zone during aseries of characterized events; determining a soil tension loss of theirrigation zone following a test irrigation event performed when theirrigation zone is near the DUL; and adding the soil tension loss to theDUL to obtain the DUL-related criterion.
 6. The process of claim 5,wherein the series of characterized events comprises at least one of aplanned irrigation event or a rainfall event.
 7. The process of claim 1,wherein the DUL-related criterion correspond to “DUL+1 irrigationevent”.
 8. The process of claim 1, wherein the DUL-related criterioncorrespond to “DUL+x irrigation event”, x being greater than 1 and aninteger or a number with a fractional component.
 9. The process of claim8, wherein when the soil water tension measurement of the irrigationzone is equal to or above the DUL-related criterion, the given volume ofwastewater applied during the irrigation event is increased by a factorcorresponding or related to x.
 10. The process of claim 1, furthercomprising characterizing a soil sample from the irrigation zone duringa startup phase to obtain a soil characterization profile of the soilsample, and wherein a maximum daily irrigation volume of wastewater isdetermined at least in part according to the soil characterizationprofile, the given volume of wastewater corresponding to a portion of amaximum daily irrigation volume of wastewater applicable to theirrigation zone.
 11. The process of claim 1, further comprisingdetermining a wastewater characterization profile of the wastewater toobtain information relative to a contaminant load of the wastewater, andwherein a maximum daily irrigation volume of wastewater is determined atleast in part according to the wastewater characterization profile, thegiven volume of wastewater corresponding to a portion of a maximum dailyirrigation volume of wastewater applicable to the irrigation zone. 12.The process of claim 1, wherein the irrigation zone comprises aplurality of irrigation zones, and the process further comprises:determining a corresponding DUL-related criterion for each irrigationzone of the plurality of irrigation zones; and obtaining a correspondingsoil water tension measurement for each irrigation zone of the pluralityof irrigation zones.
 13. The process of claim 12, wherein when more thanone corresponding soil water tension measurement is above thecorresponding DUL-related criterion, irrigating the irrigation zonehaving the largest differential between the corresponding soil watertension measurement and the corresponding DUL-related criterion.
 14. Aprocess for controlling irrigation of wastewater onto an irrigation zoneof a vegetated land, comprising: implementing a predetermined irrigationprotocol in accordance with a set of predetermined parameters toirrigate the irrigation zone during an irrigation event having a startirrigation time and an end irrigation time defining an irrigationduration, the set of predetermined parameters comprising: an irrigationschedule corresponding to a time period during which irrigation isdetermined to be suitable; a soaking time indicative of a delay betweentwo successive irrigation events in the irrigation zone; an irrigationvolume threshold indicative of a predetermined cumulative volume ofwastewater applicable onto the irrigation zone; and a DUL-relatedcriterion for the irrigation zone; wherein when at least one of thestart irrigation time is outside of the irrigation schedule, a priorirrigation time is less than the soaking time, a total daily irrigationvolume is equal or above the irrigation volume threshold, or a soilwater tension measurement of the irrigation zone is below theDUL-related criterion, no irrigation of wastewater is provided to theirrigation zone; and wherein when the start irrigation time is withinthe irrigation schedule, the prior irrigation time is equal or more thanthe soaking time, the total daily irrigation volume is below theirrigation volume threshold, and the soil water tension measurement isequal to or above the DUL-related criterion, irrigating the irrigationzone with wastewater.
 15. The process of claim 14, wherein the set ofpredetermined parameters further comprises a rainfall intensitythreshold at which or below which irrigation is determined to besuitable; and wherein when at least one of the start irrigation time isoutside of the irrigation schedule, the prior irrigation time is lessthan the soaking time, the total daily irrigation volume is equal orabove the irrigation volume threshold, the soil water tensionmeasurement of the irrigation zone is below the DUL-related criterion,or a rainfall intensity is above the rainfall intensity threshold, noirrigation of wastewater is provided to the irrigation zone; and whereinwhen the start irrigation time is within the irrigation schedule, theprior irrigation time is equal or more than the soaking time, the totaldaily irrigation volume is below the irrigation volume threshold, thesoil water tension measurement is equal to or above the DUL-relatedcriterion, and the rainfall intensity is below or equal to the rainfallintensity threshold, irrigating the irrigation zone with wastewater. 16.The process of claim 15, wherein the set of predetermined parametersfurther comprises a forecasted rainfall intensity threshold at which orbelow which irrigation is determined to be suitable; and wherein when atleast one of the start irrigation time is outside of the irrigationschedule, the prior irrigation time is less than the soaking time, thetotal daily irrigation volume is equal or above the irrigation volumethreshold, the soil water tension measurement of the irrigation zone isbelow the DUL-related criterion, the rainfall intensity is above therainfall intensity threshold, or a forecasted rainfall intensity isabove the forecasted rainfall intensity threshold in less than a givennumber of minutes, no irrigation of wastewater is provided to theirrigation zone; and wherein when the start irrigation time is withinthe irrigation schedule, the prior irrigation time is equal or more thanthe soaking time, the total daily irrigation volume is below theirrigation volume threshold, the soil water tension measurement is equalto or above the DUL-related criterion, the rainfall intensity is belowor equal to the rainfall intensity threshold, and the forecastedrainfall intensity is equal or below the forecasted rainfall intensitythreshold for a given number of minutes or the forecasted rainfallintensity is higher than the forecasted rainfall intensity threshold butafter the given number of minutes, irrigating the irrigation zone withwastewater.
 17. The process of claim 14, further comprising determininga wastewater characterization profile of the wastewater to obtaininformation relative to a contaminant load of the wastewater, whereinthe irrigation volume threshold is determined at least in part accordingto the wastewater characterization profile.
 18. The process of claim 14,wherein the irrigation volume threshold is determined at least in partaccording to a soil characterization profile of the irrigation zone. 19.The process of claim 14, further comprising determining a DUL of theirrigation zone.
 20. The process of claim 19, wherein determining theDUL of the irrigation zone comprises obtaining a series of soil watertension measurements on the irrigation zone during a startup phase thatincludes a series of characterized events.
 21. The process of claim 20,wherein the series of characterized events comprises at least one of anirrigation event or a rainfall event that is significant enough tosaturate the soil.
 22. The process of claim 14, wherein the soaking timeis determined at least in part according to a soil characterizationprofile of the irrigation zone.
 23. The process of claim 14, wherein theirrigation duration period is determined such that the soil watertension measurement remains above the DUL.
 24. The process of claim 14,wherein the predetermined irrigation protocol is repeated in alternancewith the soaking time over a period of 24 hours.